Method and apparatus for measuring the diameter of a rod-shaped article

Abstract

An apparatus and a method for measuring the diameter of at least one rod-shaped article. A beam splitter is arranged to split a beam coming from the radiation source into several component beams and to conduct the beams from different directions onto the rod-shaped article. A detection device includes a plurality of detectors each arranged to generate a signal indicating a shading of a respective one of the component beams caused by the rod-shaped article. The rod-shaped article is positioned in or guided through the beam paths between the radiation source and the detection device and the diameter of the rod-shaped article is determined from the signals generated in the detection device.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of German Application No. 10 2004 049 879.2-54, filed on Oct. 13, 2004, the subject matter of which is incorporated herein by reference. The content of each U.S. and foreign patent and patent application mentioned below is additionally incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for measuring the diameter of at least one rod-shaped article, in particular of the tobacco industry, with the aid of at least one preferably optical measuring arrangement, comprising a radiation source for generating a beam designed to irradiate the rod-shaped article, and a detection device for generating signals to indicate the shading of the beam caused by the rod-shaped article, wherein the rod-shaped article can be positioned in or can be guided through the beam path between the radiation source and the detection device and wherein the diameter of the rod-shaped article can be determined from the signals generated by the detection device. The invention furthermore relates to a method for measuring the diameter of at least one rod-shaped article, in particular of the tobacco industry, the method comprising the steps of irradiating the rod-shaped article with a preferably optical beam, generating the signals indicating the shading of the beam caused by the rod-shaped article, and determining the diameter of the rod-shaped article from these signals.

The term “rod-shaped article of the tobacco industry” in particular is understood to refer to cigarettes with or without filters, filter rods, cigarillos, cigars, and other types of smoking articles, regardless of the production stage these articles. The term “rod-shaped article” furthermore also comprises a continuous rod, which is present during a specific production stage either as a complete rod section or a divided rod section, e.g. for producing the aforementioned smoking article.

The diameter represents an essential quality feature that must be monitored during the production of cigarettes and filters. For this, the rod-shaped articles are generally aligned in the direction of their longitudinal axis and are transported either continuously or discontinuously through a measuring arrangement.

The difficulty with obtaining precise measurements of the diameter is that the rod-shaped articles are frequently “out of round,” meaning their cross sections perpendicular to the longitudinal axes deviate more or less from a circular shape.

European Patent EP 0 909 537 A1 discloses a measuring arrangement in which the radiation source generates a parallel-focused, wide beam which is reflected by 90° by a mirror onto a detection device. The rod-shaped article extends parallel to the mirror and at a right angle to the beam path and, in the process, is positioned such that a portion of the beam coming from the radiation source travels directly to the rod-shaped article while another portion of the beam arrives on the rod-shaped article after being reflected by the mirror. Thus, the beam impinging on the detection device comprises two side-by-side arranged areas of shading which represent the diameter in the form of two cross-sectional axes arranged at a right angle to each other. To be sure, this known measuring arrangement is also suitable for rod-shaped articles which do not require a rotation around their longitudinal axis or for which such a rotation is not desirable during the operation and is thus in particular suitable for continuous rods. However, measuring the diameter by only two cross-sectional axes is not precise enough in many cases.

German Patent Document DE 195 23 273 A1 furthermore describes a method and an arrangement for measuring the diameter of a rod-shaped article, in particular a cigarette, of the tobacco industry, wherein the rod-shaped article is rotated and subjected to radiation during the transport through a stationary measuring arrangement. The dimensions of the shading caused by the rod-shaped article are detected accordingly, are converted to an electric measuring signal, and a signal for the diameter of the rod-shaped article is generated from several such measuring signals. To be sure, the measuring accuracy can be increased with this known arrangement, but the known arrangement in particular is not suitable for measuring the diameter of a continuous rod which does not rotate around its longitudinal axis.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and an apparatus of the aforementioned type which permits extremely accurate diameter measurements of rod-shaped articles, without having to subject the measuring arrangement and the rod-shaped articles to a rotating movement and which is therefore particularly suitable for diameter measurements on continuous rods.

The above and other objects are accomplished according to a first aspect of the invention wherein there is provided an apparatus for measuring the diameter of a rod-shaped article, comprising: a radiation source for generating a beam; a beam splitter arranged to split the beam coming from the radiation source into several component beams and to conduct the beams from different directions onto the rod-shaped article; and a detection device including a plurality of detectors each arranged to generate a signal indicating a shading of a respective one of the component beams caused by the rod-shaped article, wherein the rod-shaped article is positioned in or guided through the beam paths between the radiation source and the detection device and the diameter of the rod-shaped article is determined from the signals generated in the detection device.

According to a second aspect of the invention, there is provided a method for measuring the diameter of a rod-shaped article, comprising: generating a beam of radiation; splitting the beam into several component beams that are conducted from different directions onto the rod-shaped article; generating separate signals each of which indicate a shading of a respective one of the component beams caused by the rod-shaped article; and determining the diameter of the rod-shaped article from the signals.

The invention accordingly consists of using a corresponding number of component beams, obtained by splitting the (main) beam generated by the radiation source, for a plurality of diameter measurements of the rod-shaped article. Each measurement occurs from a different perspective since the component beams according to the invention are guided from different directions onto the rod-shaped article. The higher the number of component beams used and the number of resulting measurements, the higher the precision for determining the cross-sectional shape of the rod-shaped article.

An advantages achieved with the invention is that the diameter of the rod-shaped article can be determined with extreme accuracy, in particular for rod-shaped articles that are not round while. Another advantage is that a rotational movement of the measuring arrangement or a rotation of the rod-shaped article around its longitudinal axis is not required and the measurement according to the invention therefore does not require rotating components. The invention is therefore especially suitable for use in cases where a rotational movement in particular is not required or even desired for the processing, and thus the invention is suitable, in particular, for continuous rods.

As a result of the latter, the rod-shaped article can remain immovable during the measurement. Alternatively, it is also conceivable and especially advantageous for the operation if the rod-shaped article is moved continuously or discontinuously in a longitudinal axial direction through the measuring arrangement, wherein during one stage of the production of the rod-shaped articles, a continuous rod can be present, which can be transported in the longitudinal axial direction through the measuring arrangement, either as a single continuous rod section or as already divided continuous rod sections.

Owing to the fact that the invention permits a nearly infinite number of diameter measurements at one and the same location of a rod-shaped article, it is also possible to detect the cross-sectional shape and the ‘out of roundness,’ as well as the minimum and maximum diameter of the rod-shaped article. The latter is particularly important for determining whether the diameter is still within permissible limits. The invention furthermore can be used particularly advantageously for measuring cigarettes and filter plugs having an elliptical cross section, so that matching filter plugs and cigarette rods can be detected.

The beam splitter advantageously guides the component beams onto the rod-shaped article so that each component beam is shaded only partially by the rod-shaped article. The detection device thus detects side-by-side arranged light-dark transitions of the component beams, arriving from different directions on the rod-shaped article, from which the diameter and/or thickness of the rod-shaped article can be determined, respectively in the directions perpendicular to the component beams.

The diameter of the rod-shaped article is generally determined from the signals coming from the detection device in an evaluation unit, installed downstream of the detection device. An average-value former in the evaluation unit is preferably used to form an average value of the signals coming from the detecting means.

According to one exemplary embodiment, the beam splitter is provided with mirrors which deflect at least some of the component beams of the main beam in different directions and then onto the rod-shaped article. As an alternative or in addition, at least one prism can be provided with at least one mirror surface which correspondingly deflects at least some of the component beams. The component beams are thus separated out of the main beam with the aid of the mirrors and/or the mirror surface(s).

It a further exemplary embodiment, there is provided a beam-recombination device, which recombines the component beams after they pass the rod-shaped article, so that they again form a single beam in which the component beams are essentially arranged parallel to each other. The detectors in this case are substantially arranged side-by-side in a row. A particularly simple embodiment of the detection device is possible with this design since it is structurally very easy to combine the side-by-side arranged detectors. The beam-recombination device is preferably also provided with mirrors and/or at least one prism, comprising at least one mirror surface, such that it is particularly easy to redirect the component beams to the same direction.

A device for the substantially parallel alignment of the beam coming from the radiation source may be provided between the radiation source and the beam splitter. A device of this type is particularly useful if the radiation source generates a diverging beam, as is generally the case. Using such a device can also simplify the splitting of the beam into component beams since only the individual parallel sections of the main beam must be separated out to form component beams, owing to the parallel alignment. A device of this type is preferably provided with a collimator lens. A cylindrical lens can furthermore be installed downstream of the device and can be used advantageously for generating component beams.

A laser, in particular a laser diode, can advantageously be used as a radiation source and/or the detecting means can be charge-coupled device elements.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the invention will be further understood from the following detailed description of the preferred embodiments with reference to the accompanying drawings.

FIG. 1 shows a perspective, schematic view of a continuous cigarette rod machine, showing the essential structural components.

FIG. 2 shows a schematic view of a first exemplary embodiment according to the invention of an optical measuring arrangement with its essential components, used in the continuous cigarette rod machine shown in FIG. 1, which is positioned at a right angle to the longitudinal axis and movement direction of the continuous cigarette rod.

FIG. 3 shows a schematic view of a second exemplary embodiment according to the invention of an optical measuring arrangement with its essential components, used in the continuous cigarette rod machine shown in FIG. 1, which is positioned at a right angle to the longitudinal axis and movement direction of the continuous cigarette rod.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic, perspective view of a continuous cigarette rod machine of the type “PROTOS,” manufactured by the assignee of the present invention, in which the main components are visible. The design and function of this continuous cigarette rod machine are briefly described in the following.

An airlock 1 supplies a pre-distributing device 2 with batches of tobacco. In a controlled operation, a withdrawing roller 3 of the pre-distributing device 2 is used to supplement the tobacco in a storage container 4 from which a vertical conveyor 5 removes the tobacco. In a controlled operation, the vertical conveyor then feeds this tobacco to an accumulation chute 6. A pin roller 7 removes a uniform stream of tobacco from this accumulation chute 6 and a beater roller 8 then beats the tobacco out of the pins of the pin roller 7 and tosses the tobacco with a constant speed onto a circulating distributing web 9.

A fibrous tobacco fleece, formed in this way on the distributing web 9, is subsequently tossed into a sifting device 11 which essentially consists of an air curtain through which larger and/or heavier tobacco particles pass while all other tobacco particles are directed by the air into a funnel 14 that is formed by a pin roller 12 and a wall 13. From the pin roller 12, the tobacco is tossed into a tobacco channel 16 and onto a continuous rod conveyor 17 against which the tobacco is held by air suctioned into a low-pressure chamber 18, to form a continuous tobacco rod.

A straightening device 19 removes excess tobacco from the continuous tobacco rod which is then placed onto a synchronously conveyed cigarette-paper strip 21. The cigarette-paper strip 21 is pulled from a bobbin 22, is guided through a printing device 23, and is then placed onto a driven format belt 24. The format belt 24 transports the continuous tobacco rod and the cigarette-paper strip 21 through a format machine 26 in which the cigarette-paper strip 21 is folded around the continuous tobacco rod, so that one edge still sticks up. This edge is coated with glue by means of a glue applicator, not shown herein, whereupon the glue seam is closed and dried by means of a tandem seam smoothing iron 27.

A continuous cigarette rod 28, formed in this way, passes through a measuring and control unit 29 and is cut into double-length cigarettes 32 with a knife apparatus 31. The double-length cigarettes 32 are then transferred onto a takeover drum 36 of a filter-tipping machine 37 by means of a transfer device 34 with controlled arms 33. On the cutting drum 38 of the filter-tipping machine, they are cut with a circular knife into individual cigarettes.

Conveying belts 39, 41 convey excess tobacco into a container 42, arranged below the storage container 4, from which the returned tobacco is removed again with the aid of the vertical conveyor 5.

The measuring and control unit 29 of the continuous cigarette rod machine according to FIG. 1 is provided with an optical measuring arrangement, of which a first exemplary embodiment 50 is shown in FIG. 2 and a second exemplary embodiment 50a is shown in FIG. 3.

The optical measuring arrangement 50 according to FIG. 2 comprises a radiation source 52, which is preferably provided with at least one laser diode or consists of such a laser diode. The radiation source 52 for the exemplary embodiment shown in FIG. 2 is designed to generate a diverging beam 54a. The diverging beam 54a is converted with the aid of a downstream-arranged collimator lens 56 to a parallel beam 54b, which then passes through a cylindrical lens 58.

Behind the cylindrical lens 58, the parallel beam 54b, which can be called a main beam in the same way as the beam 54a, is split into component beams 601 to 608 that impinge from different directions onto the continuous cigarette rod 28, such that each component beam is shaded only partially by the continuous cigarette rod 28. In the process, the continuous cigarette rod 28 is guided through the optical measuring arrangement 50 so that the component beams 601 to 608 extend approximately at a right angle to the longitudinal axis, which extends at a right angle to the drawing plane for FIG. 2, thus causing the component beams to extend at a right angle to the movement direction of the continuous cigarette rod 28.

FIG. 2 furthermore shows that the component beams 601 to 608 initially form side-by-side arranged parallel beam sections of the main beam 54b, directly behind the cylindrical lens 58. The component beams 601 to 608 of the exemplary embodiment are subsequently reflected on mirrors, wherein some of the component beams are deflected only after they impinge on the continuous cigarette rod 28 and other component beams are deflected before they impinge on the continuous cigarette rod 28.

The first component beam 601, the ‘upper’ component beam in FIG. 2, is initially deflected by 45° on a mirror 621 and onto a mirror 641, where it is deflected by 90° onto the continuous cigarette rod 28. In the same way, the adjacent second component beam 602 is initially deflected by 45° on a mirror 622 and subsequently by 90° on a mirror 642 in the direction of the continuous cigarette rod 28. While the mirrors 621 and 622 are arranged side-by-side, such that the first and second component beams 601 and 602 continue to extend parallel following the reflection, the two mirrors 641 and 642 are spaced apart such that the first component beam 601 grazes one side of the continuous cigarette rod 28 and the second component beam 602 grazes the opposite side of the continuous cigarette rod 28. Accordingly, the spacing between the two mirrors 641 and 642 is determined by the thickness of the continuous cigarette rod 28. However, the orientation of the mirrors 641 and 642 relative to each other is identical, so that these mirrors 641 and 642 are aligned parallel.

The third component beam 603 is reflected by 90° on a mirror 623 and subsequently impinges directly onto the continuous cigarette rod 28. The same happens with the fifth component beams 605, which is deflected on a mirror 625. As a result, the third component beam 603 and the fifth component beam 605 are aligned parallel when they pass the continuous cigarette rod 28, with the third component beams 603 grazing one side of the continuous cigarette rod 28 and the fifth component beam 605 grazing the opposite side of the continuous cigarette rod 28. The two mirrors 623 and 625 are accordingly spaced apart, but have the same orientation. Thus, upon their arrival on the continuous cigarette rod 28, the third component beam 603 and the fifth component beam 605 extend at an angle of 45° relative to the first component beam 601 and the second component beam 602.

The fourth component beam 604 and the sixth component beam 606 also form a pair and pass the continuous cigarette rod 28 at a right angle, relative to the first component beam 601 and the second component beam 602. For this, the fourth component beam 604 is reflected on a mirror 624 and the sixth component beam 606 is reflected on a mirror 626 by 45° in the direction of the continuous cigarette rod 28, wherein the two mirrors 624 and 626 extend parallel to each other, but are spaced apart such that the fourth component beam 604 grazes the continuous cigarette rod 28 on one side and the sixth component beam 606 grazes the continuous cigarette rod 28 on the opposite side.

In contrast to the component beams 601 to 606, the seventh component beam 607 and the eighth component beam 608 are focused by means of the cylindrical lens 58 directly onto the continuous cigarette rod 28 before being reflected by the mirrors 627 and/or 628 which are installed behind continuous cigarette rod 28. The seventh component beam 607 and the eighth component beam 608 are spaced apart for this, such that the seventh component beam 607 grazes the continuous cigarette rod 28 on one side and the eighth component beam 608 grazes the continuous cigarette rod 28 on the opposite side. The spaced-apart seventh and eighth component beams 607 and 608, which are not subjected to a change in direction before they pass by the continuous cigarette rod 28, therefore extend at an angle of 135° to the first and second component beams 601 and 602.

For the exemplary embodiment shown herein, the parallel component beams 601 to 608 have the same constant cross section over their course. However, configurations with changing cross sections for the component beams are also conceivable as well, for example following a reflection on a mirror. It is furthermore conceivable, in principle, to form converging or diverging beams if necessary.

Owing to the previously described course of the component beams 601 to 608, a partial shading of the continuous cigarette rod 28 occurs over an angular region of approximately 90° for the exemplary embodiment, wherein the shaded angular regions overlap, as shown in FIG. 2.

Of course, the width and the spacing between component beams can be adjusted through a corresponding configuration of the reflecting mirrors, so as to shade an angular region of less than 90°. However, the angular shading region selected for the exemplary embodiment, which uses eight component beams for irradiating the continuous cigarette rod 28, should not be less than 45° because undesirable gaps in the form of non-shaded regions can otherwise develop. The angular region to be shaded should furthermore not exceed 180° to prevent an undesirable overlapping of two parallel component beams belonging to the same pair, thus making it difficult or even impossible to assign these clearly.

FIG. 2 shows that the component beams directly behind the cylindrical lens 58 are defined so that the first to the sixth component beams 601 to 606 are positioned directly adjacent to each other while the seventh component beam 607 is at a distance from the sixth component beam 606 as well as at a distance from the eight component beam 608, wherein FIG. 2 shows that the distance respectively corresponds to the width of a component beam. The gap between the sixth component beam 606 and the seventh component beam 607, as well as the gap between the seventh component beam 607 and the eighth component beam 608 furthermore contains beam sections belonging to the main beam 54a which, in the same way as the component beams 601 to 608, represent component beams. However, these component beams are not used further because the beam section between the sixth component beam 606 and the seventh component beam 607 is reflected back by the mirror 641, directly onto the cylindrical lens 58, while the beams section between the seventh component beam 607 and the eight component beam 608 is completely shaded by the continuous cigarette rod 28. Accordingly, the exemplary embodiment does not make use of the complete width of the main beam 54b for forming the relevant component beams 601 to 608. It should be noted here that other configurations are conceivable, of course, which use a higher or lower number of component beams for the partial shading of the continuous cigarette rod 28. For example, it is also possible to use all beam sections of the main beam 54b to form the relevant component beams.

FIG. 2 furthermore shows that the individual mirrors are configured such that their effective cross section for reflection does not exceed the cross section of the partial beam they reflect, so as to prevent interference between the respectively adjacent component beam. As a result, the mirrors with the smaller reflection angles (e.g. the mirrors 621, 622, 624, 626) have a greater length than the mirrors with the higher reflection angles (e.g. 623, 625, 641, 642).

In place of the discrete mirrors shown in FIG. 2, it is furthermore possible to use an optical element having reflective surface areas incorporated therein. Of course, it is also conceivable to use prisms or the like in place of mirrors.

FIG. 2 and the preceding description clearly show that the mirrors 621, 622, 623, 624, 625 and 626 also function as beam splitters. The same is true for the mirror 627 on which the seventh component beam 607 is reflected by an angle of 90° (downward according to FIG. 2) after it has passed the continuous cigarette rod 28, and the mirror 628 on which the eighth component beam 608 is also reflected by 90° after passing the continuous cigarette rod 28 (downward according to FIG. 2). The mirrors 621 to 628 consequently form a beam splitter for the embodiment shown herein.

FIG. 2 furthermore shows that the component beams 601 to 608 of the exemplary embodiment are recombined later on to form a single beam by using additional mirrors and are then conducted to the detector row 66. As a result of the above-described arrangement of the mirrors 641 and 642 and after passing the continuous rod 28, the first component beam 601 and the spaced apart, parallel second component beam 602 are conducted at a right angle directly onto the detector row 66. For the third component beam 603 and the parallel, spaced apart fifth component beam 605, the mirrors 643 and 645 are provided between the continuous cigarette rod 28 and the detector row 66, on which these component beams are reflected by about 45° before impinging at a right angle on the detector row 66. Since the fourth component beam 604 and the parallel, spaced apart sixth component beam 606 extend approximately parallel to the detector row 66 while passing the continuous cigarette rod 28, the additional mirrors 644 and 646 are provided for deflecting these partial beams by 90° in the direction of the detector row 66, wherein the embodiment shown herein respectively requires two additional mirrors 627, 647 and 628, 648 for redirecting the seventh component beam 607 and the eight component beam 608, which are arranged in the beam path after the continuous cigarette rod 28. Initially, the seventh and/or the eighth component beam 607 and/or 608 are reflected by 90° on the mirror 627 and/or 628 (downward according to FIG. 2), before they are reflected again by 45° on the mirror 647 and/or 648 in the direction of the detector row 66.

The mirrors 641 to 648 accordingly function as a beam-recombination device for a parallel, side-by-side alignment of the component beams 601 to 608, such that they form a single beam which impinges perpendicular on the detector row 66. It is apparent from FIG. 2 that the sequence of the individual component beams 601 to 608 is different when they impinge on the detector row 66 than when they exit the cylindrical lens 58. However, this fact does not play a role in the determination of the diameter. Of course, configurations with a different sequence for the component beams are conceivable as well.

The component beams 601 to 608 for the embodiment shown herein are deflected by 135° from the start to the end of their beam path before impinging on the detector row 66. Of course, a different orientation for the detector row 66 is also conceivable.

With respect to possible alternative configurations for the mirrors 641 to 648, the same applies as previously stated for the mirrors 621 to 628.

FIG. 3 shows a second preferred embodiment of a measuring arrangement 50a which differs from the measuring arrangement 50 shown in FIG. 2 in that three separate prisms 72, 74 and 76 are provided in place of discrete mirrors while the remaining components are the same as for the embodiment of the optical measuring arrangement 50 shown in FIG. 2. Thus, only the differences to the first embodiment according to FIG. 2 are described in the following for the second embodiment of the optical measuring arrangement 50a according to FIG. 3.

The three separate prisms 72, 74, 76 are provided for splitting the main beam and aligning and recombining the component beams, wherein the prisms 72, 74, 76 are designed such that the component beams enter and exit the surface areas at a ninety degree angle to avoid diffraction effects.

In contrast to the first embodiment according to FIG. 2, the parallel beam 54b of the second embodiment of the optical measuring arrangement 50a, shown in FIG. 3, is divided not into eight but into six component beams 601 to 606 behind the cylindrical lens 58.

The first component beam 601, the ‘top’ component beam in FIG. 3, initially enters the first prisms 72 through a first surface 721, aligned at a right angle, is then reflected by an opposite-arranged second surface 722 of the first prism 72, arranged at an angle of 1200 relative to the impinging component beam, in the direction of the continuous cigarette rod 28 and exits the prism 72 again through a third surface 723, aligned at a right angle, such that it grazes one side of the continuous cigarette rod 28. Following this, the first component beam 601 enters a surface 761, aligned at a right angle, of the third prism 76 and exits again through an also right-angle aligned second surface 762 before it impinges on the detector row 66. In the same way, the neighboring component beam 602 is deflected by the first prism 72 and is conducted through the third prism 76, wherein the second component beam 602 is spaced apart from the first component beam 601, such that the second component beam 602 grazes the continuous cigarette rod 28 on its opposite side.

The third component beam 603 enters the second prism 74 through its right-angle aligned first surface 741, is reflected by an opposite arranged second surface 742 of the second prism 74, arranged at an angle of 1500 relative to the impinging component beam, and exits again through its third surface 743, positioned at a right angle to the component beam, in the direction of the continuous cigarette rod 28, such that it grazes this rod on one side. Subsequently, the third component beam 603 enters the third prism 76 through a third surface 763, arranged at a right angle to this component beam, is reflected by an opposite-arranged fourth surface 764, positioned at a 1500 angle relative to the impinging component beam, and exits the third prism 76 through its second surface 762, which extends at a right angle to this component beam, such that it arrives at the detector row 66. The fourth component beam 604 extends parallel to the third component beam 603 and thus follows the same course, but at a distance to the third component beam 603 and grazes the continuous cigarette rod 28 on the opposite side.

The fifth component beam 605 passes through the second prism 74 without being reflected by entering the second prism 74 through its first surface 741, positioned at a right angle to the component beam, and exits the second prism 74 again through its fourth surface 744, which is also aligned at a right angle to the component beam, such that it grazes the continuous cigarette rod 28 on one side. Following this, the fifth component beam 605 enters the first prism 72 through a fourth surface 724, also positioned at a right angle, is then reflected by its slanted second surface 722 and exits again through its fifth surface 725, arranged at a right angle to the component beam, such that it impinges on the detector row 66. The same course is also followed by the sixth component beam 606, which is conducted parallel to the fifth component beam 605, but at a distance thereto, and grazes the continuous cigarette rod 28 on the opposite side.

Similarly to the first embodiment shown in FIG. 2, the first and second component beams 601 and 602, the third and fourth component beams 603 and 604, as well as the fifth and sixth component beams 605 and 606 respectively form pairs which have the same alignment and take the same course.

FIG. 3 and the associated specification text clearly show that the three prisms 72, 74, 76 take on the function of a beam splitter for splitting the parallel beam 54b into several—here six—component beams 601 to 606, which are then conducted from different directions onto the continuous cigarette rod 28. The prisms also function as a beam-recombination device for recombining the individual component beams 601 to 606 in a parallel, side-by-side alignment to form a single beam that impinges with a ninety degree angle on the detector row 66.

With respect to additional features and characteristics, reference is made to the description of the first exemplary embodiment of the optical measuring arrangement 50, shown in FIG. 2, to avoid repetition.

The detector row 66 comprises several side-by-side positioned detecting elements, wherein respectively one detecting element is assigned to one component beam. However, it is also conceivable to have several detecting elements which respectively combine to form a group which is then assigned to a defined component beam. It is advantageous if the detecting elements are charge-coupled device elements.

The light-dark transitions of the component beams, which impinge from different directions on the continuous cigarette rod 28, are projected side-by-side onto the detector row 66. These light-dark transitions are indicated schematically in FIG. 2, in a graph assigned to the detector row 66.

An evaluation unit 81 (shown in FIG. 2) which is positioned downstream of the detector row 66 then computes the diameter of the continuous cigarette rod 28 from the light-dark transitions, respectively in the directions extending perpendicular to the component beams. In this way, a precise measurement of the thickness of the continuous cigarette rod 28 is obtained for various angular directions. The thickness of the continuous cigarette rod 28 can be determined over a 90° range since eight component beams 601 to 608 combined into four pairs are used for the first embodiment shown in FIG. 2. Accordingly, the continuous cigarette rod 28 for the first embodiment according to FIG. 2 is measured in four different directions. FIG. 3 shows that only six component beams 601 to 606, combined into three pairs, are used for the second embodiment, wherein the thickness can be determined over a 120° range. For that reason, the continuous cigarette rod 28 is measured in only 3 directions for the second embodiment according to FIG. 3.

If the number of component beams increases, a larger number of measurements at a smaller angle division can be realized, thus making it possible to increase the accuracy even further. In contrast, a reduction in the number of component beams leads to a lower number of measurements over a larger angular distance.

Finally, the evaluation unit can also comprise an average-value former 83 for forming the average value of the signals from the detector row 66, so as to determine an average value for the diameter of the continuous cigarette rod 28.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

Claims

1. An apparatus for measuring the diameter of a rod-shaped article, comprising:

a radiation source for generating a beam;

a beam splitter arranged to split the beam coming from the radiation source into several component beams and to conduct the beams from different directions onto the rod-shaped article; and

a detection device including a plurality of detectors each arranged to generate a signal indicating a shading of a respective one of the component beams caused by the rod-shaped article,

wherein the rod-shaped article is positioned in or guided through the beam paths between the radiation source and the detection device and the diameter of the rod-shaped article is determined from the signals generated in the detection device.

2. The apparatus according to claim 1, wherein the beam splitter conducts the component beams onto the rod-shaped article so that each component beam is only partially shaded by the rod-shaped article.

3. The apparatus according to claim 1, further including an evaluation unit coupled to the detection device to determine the diameter of the rod-shaped article based on the signals generated by the detection device.

4. The apparatus according to claim 3, wherein the evaluation unit includes an average-value former to form an average value from the signals generated by the detecting means.

5. The apparatus according to claim 1, wherein the beam splitter includes mirrors that deflect at least some of the component beams of the main beam so such that the component beams impinge from different directions on the rod-shaped article.

6. The apparatus according to claim 1, wherein the beam splitter comprises at least one prism that deflects at least some of the component beams of the main beam, such that the component beams impinge from different directions on the rod-shaped article.

7. The apparatus according to claim 1, further including a beam re-combination device arranged to recombine the component beams after they impinge on the rod-shaped article into a single beam in which the component beams are substantially parallel to each other, wherein the detectors are essentially aligned side-by-side in a row.

8. The apparatus according to claim 7, wherein the beam re-combination device comprises mirrors that redirect the component beams to the same direction.

9. The apparatus according to claim 7, wherein the beam re-combination device comprises at least one prism that redirects the component beams to the same direction.

10. The apparatus according to claim 1, further including an alignment device positioned between the radiation source and the beam splitter to substantially parallel align the beam coming from the radiation source.

11. The apparatus according to claim 10, wherein the alignment device comprises a collimating lens.

12. The apparatus according to claim 10, further including a cylindrical lens arranged downstream of the alignment device.

13. The apparatus according to claim 1, wherein the radiation source comprises a laser.

14. The apparatus according to claim 12, wherein the laser comprises a laser diode.

15. The apparatus according to claim 1, wherein the detectors comprise charge-coupled device elements.

16. The apparatus according to claim 1, wherein the beam is an optical beam.

17. A method for measuring the diameter of a rod-shaped article, comprising:

generating a beam of radiation;

splitting the beam into several component beams that are conducted from different directions onto the rod-shaped article

generating separate signals each of which indicate a shading of a respective one of the component beams caused by the rod-shaped article; and

determining the diameter of the rod-shaped article from the signals.

18. The method according to claim 17, wherein the splitting step includes conducting the component beams onto the rod-shaped article so that each component beam is shaded only partially by the rod-shaped article.

19. The method according to claim 17, further including recombining the component beams, after impinging on the rod-shaped article, to form a single beam in which the component beams are aligned substantially parallel to each other.

20. The method according to claim 17, and further including forming an average value from the signals generated by the different component beams.

21. The method according to claim 17, further including aligning the beam to be parallel before being split into component beams.

22. The method according to claim 17, wherein the step of generating a beam includes generating an optical beam.