CA1154473A

CA1154473A - Method and an arrangement for the feed of a material web

Info

Publication number: CA1154473A
Application number: CA001154473A
Authority: CA
Inventors: Lars Carlsson
Original assignee: Tetra Pak International AB
Current assignee: Tetra Pak AB
Priority date: 1979-12-11
Filing date: 1980-12-10
Publication date: 1983-09-27
Also published as: JPH0310495B2; EP0030366B1; DK149406B; AU6524280A; BR8008070A; ES8202313A1; AU536006B2; SE7910167L; NO149129B; FI803842L; FI66788B; MX153824A; SE443128B; EP0030366A1; ATE4886T1; DK149406C; DE3065208D1; NO803707L; US4351461A; FI66788C

Abstract

ABSTRACT OF THE DISCLOSURE

The feed of a web provided with a pattern can be effected using a rotating driver. When the feed is to be synchronous with a processing operation, or when for other reasons the feed must take place in register, the feed up to now has been monitored and corrected by photocell equip-ment and photocell marks made on the web. In the case of webs which are provided with transverse crease lines, as is customary for example in the packaging industry, the feed as well as the keeping in register may be effected in accordance with the invention using a feed mandrel which engages with the transverse crease lines of the web by means of a number of edges arranged around the circumfer-ence of the mandrel. Any faults in the mutual distance between the transverse crease lines are corrected auto-matically by the mandrel, and any special monitoring or subsequent correction of the feed is not necessary.

Description

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The present invention relates to a method for feeding a web provided with transverse crease lines by a rotating driver whic~ engages with the crease lines by edges arranged around its circumference.

The present invention also relates to an arrangement for the feed of a web provided with transverse crease lines by means of a rotating driver which has axial edges distri-buted around its circumference adapted to engage with the crease lines.

Packages of a variety of different types are often manu-factured from a semi-rigid plastic, paper or cardboard mater-ial which is supplied to an automatic machine and, whilst being fed stepwise through the machine, is successively con-verted into a finished package. In the manufacture of pack-ing containers e.g. for liquid foodstuffs, such as milk, the machine is supplied with a weblike, laminated material. The material is relatively rigid, but flexible, and comprises a central carrier layer of paper which is coated at least on one side with a homogeneous plastic layer. To facilitate - the folding of the material necessary for the conversion to finished packing containers, the web is provided with a re-gularly recurring pattern of weakening or crease lines, along which the folding of the material will afterwards take place. The feed of the web occurs intermittently or continu-ously, but at varying speed according to a predetermined cycle in rhythm with the conversion of the web to individual packing containers. It is a prerequis-ite for the process-ing of the web and conversion of the same into individualpacking container to take place that the web must always be fed to an exactly predetermined position wherein the process-ing or the shaping is carried out, since otherwise the fold-ing of the web will not take place along the crease lines mentioned earlier. An accurately defined length of feed which guides the web to a correct position is important also . ~

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for other reasons, e.g. in the cases when the material is to be provided with opening arrangements or with a printed pattern which has to be placed so that it will be in correct position on the finished packing container.

The feed of a web provided with crease llnes, patterns or other irregularities in the aforementioned manner is called feed in register, and occurs very often in package manufacture. The most common method for ensuring a suffi-ciently accurate keeping in register is to provide the webwith a repeated pattern of photocell marks, e.g. printed dots or lines of contrasting colour, which pattern is in an accurately defined relation to the crease line pattern, print pattern or the like of the web. Using photocells co-operat-ing with the said photocell marks the feed, which may takeplace with the help of driver elements in the form of rollers, feed jaws or the like, is then monitored and continuously corrected so that a good keeping in register is achieved and maintained. Such a correcting system also has the advantage that any inaccuracies in the crease line pattern, that is to say small deviations from the specified nominal dimension between transverse crease lines following upon each other exercize no negative effect. However, the system is compli-cated in its setup, and consequently also contains presump-tive sources of error. It is a further disadvantage that theaccuracy of the keeping in register will depend directly on the accuracy with which the photocell marks are applied to the material web (in relation to the crease line pattern).

The present invention provides a method for the feeding of a web provided with transverse crease lines in register, which method is simple and uncomplicated and renders unneces-sary special marks on the material web made for keeping in register.
The present invention also provides a method of eed ~æ~

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which automatically ensures that the feed takes place in re-gister independently of the faults which may exist in the distance between transverse crease lines of the web.

According to the present invention there is provided a method for feeding a web provided with transverse crease lines using a rotating driver which by means of edges around its circumference engages with the crease lines, the linear distance between two crease lines for engagement with the driver being reduced by temporary bending of the web there-between so that each of the crease lines engages with its edge.

Thus in accordance with the invention the linear dis-tance between two crease lines intended for engagement with the driver is reduced through temporary bending of the web therebetween, so that each of the crease lines engages with its edge.

Suitably the bending is effected by a vacuum which is desirably applied during a limited part of the rotation of the driver. Suitably the reduction of the length of the web is adjusted by varying the degree of vacuum to the suc-tion cup.
The present invention also provides an apparatus for the feed of a web provided with transverse crease lines in register which arrangement is not affected by the previous disadvantages.
The present invention further provides a feed apparatus which is simple and uncomplicated and which by direct machan-ical engagement with the transverse crease lines of the web fed ensures that the feed is taking place in register with the crease line pattern, independently of the deviations which occur ~n the nominal distance between consecutive transverse crease lines. ~
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The present invention thus provides an apparatus for feeding of a web provided with transverse crease lines by means of a rotating driver which has axial edges distributed around its circumference for enga~ement with the crease lines, the distance between two consecutive edges on the driver is less than the corresponding distance between crease lines of the web, elements being arranged so as to bend the part of the web between the edges to such an extent that the crease lines coincide with the edges.
Thus in accordance with the present invention the dis-tance between two consecutive edges on the driver is less than the corresponding distance between crease lines of the web, elements being arranged so as to bend the part of the web between the edges to such an extent that the crease lines coincide with the edges.

Suitably the parts of the driver situated between the edges are recessed in relation to the plane wherein two edges adjoining each other are situated, and desirably the driver has suction heads located in the recessed areas. Pre-ferably each of the suction heads has a flexible collar whose free end, when not acted upon, substantially touches the said plane. Suitably the suction heads are movable be-tween a front position, wherein they project outside thesaid plane, and a rear position, wherein they are drawn into the recessed area situated between the edges. Desirably the apparatus includes a movable counter device for pressing the material web into the space hetween the edges. Preferably the edges of the driver element are formed by adjustable rules.

The method and the apparatus in accordance with the in-vention make it possible, directly in connection with the feed and using the actual feed element, to overcome the effect of a faulty distance between consecutive transverse - 3a -.' .~`~

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crease lines on the web so that the web never comes out ofregister. By desi~ning the driver so that the distance be-tween two consecutive edges is always less than the smallest accepted distance between the transverse crease lines co-operating with the driver on the web which is to be used,and by shortening the linear distance between the crease lines co-operating with the said edges by bending in connec-tion with the feed, the said crease lines are always fixed straight before the corresponding edges on the driver, so that the latter on rotating a certain predetermined part of a turn always displaces the web to a predetermined position, whereupon the cycle is repeated.

The method and the apparatus in accordance with the invention will be described in greater detail in the follow-ing with special reference to the enclosed schematic drawing which is a side elevation of the arrangement in accordance with the invention and only shows the details necessary for the understanding of the invention.
; 20 In the Figure is shown a feed element in the form of a rotating driver 1 which is mounted on a horizontal central axle. The driver 1 can be actuated by a motor and is in-stalled in a packing machine (not shown) for the feed of a packing material web 2 which is to be processed in the machine. The packing material web is a laminated material which comprises a central carrier layer of paper, coated on both sides with homogeneous plastic material. The packing material web 2 is thus relatively rigid and in order to facilitate the necessary folding of the web when converting the web to packing containers, . ;
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the web is provided with a pattern of folding or crease lines, which is constituted of linear indentations in the material. Beside longitudinal crease lines and those ex-tending obliquely across the web, not shown on the draw-ing, the web has transverse crease lines 3 extending trans-versely over the web at equal intervals, which in accor-dance with the invention are also made use of for the feed of the web.

The rotating driver 1 is of a substantially square cross-section and has four mutually parallel edges 4 which are arranged at an equal pitch around the driver. Between the edges 4 the driver sides are recessed, and in each re-cess one or more pneumatic suction heads 5 are provided.
At some distance from the driver 1 a cylindrical guide roller 6 is provided which can rotate about a horizontal axle. The guide roller 6 is situated below the driver and extends slightly inwards underneath the same so that the part of the web 2 which runs from the guide roller 8 to the driver 1 will always be between the driver and the vertical plane extending through the edge 4 towards which the web runs at the current instant, that is to say the angle a in the Figure is always greater than 0.
A further cylindrical roller 7, whose centre axle is parallel with the guide roller 6, is in contact with the guide roller 6. The roller 7 can be braked by means of some adjustable electrical or mechanical device and the material web 3 running in the nip between the rollers 6 and 7 can be braked thereby, so that it is kept taut whilst running from the guide roller 6 to the current edge 4 of the driver. The remaining part of the web 2, that is to say the part extending over the driver and the part which already has passed the driver is kept taut with the help of another device (not shown), e.g. a driving roller which can be rotated by means of an adjustable motor.

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The drivin~ of the web in register by the method and apparatus in accordance with the invention takes place by stepwise rotation of the driver 1 in the direction of the arrow 8. The web 2 follows this rotation, because it en-wraps such a large part of the circumference of the driver1, that always at least two of the edges 4 of the driver engage with the crease lines 3 extending transversely over the web 2, and this prevents any sliding of the web in relation to the driver. On the assumption that the web running over the driver is kept taut and that th~e distance between two adjoining edges 4 on the driver corresponds exactly to the distance between two transverse crease lines 3 following one another on the web, the feed or the web can be accurately controlled by the driver, since the rotation of the latter over a predetermined number of de-grees corresponds to the feed of the web over a predetermin-ed length. However, it is not possible to provide the web

2 with crease lines 3 with such precision that the distance between the crease lines following one another is exactly the same length over the whole length of the web 2. Since even a very small fault in the distance between the crease lines following upon each other will gradually accumulate and together with earlier faults will cause the engagement between the crease lines and the edges 4 to be lost, and eventually the web to come out of register, it is necessary that during each feed such a correction is performed that the effect of the faulty distance on the feed is eliminated.
This is achieved in accordance with the invention by reduc-ing the linear distance between two crease lines 3 intended for engagement with the driver 1 by means of temporary bending of the web situated between lines until each of the crease lines engages with its edge 4 on the driver. When determining the distance between two edges 4 on the driver situated next to each other, it is necessary first to determine the greatest possible deviation '7;~

from the nominal distance between two consecutive crease lines on the web which can be tolerated in the manufac-ture of the material. The driver is then designed so that the distance between two consecutive edges i5 a little less than the correspondin~ distance between crease lines

3 of the web, when these are at the shortest distance from each other which is accepted in the manufacture of the material. When the web i5 fed by the driver 1 the linear distance between the crease lines 3 is then reduced, in that the part of the web situated between the edges 4, through the effect of vacuum is drawn down into the recess in the driver until the crease lines 3 engage with the respective edge 4. In this manner the part of the web be-tween the crease lines 3 is centred in relation to the side of the driver situated between the edges 4, so that the crease line 3 which last has come into contact with the driver is brought into the correct position over the current edge 4, and by repeating this procedure during each feed, the material is placed each time into a de-fined position. Variations in the distance between twoconsecutively situated crease lines 3 are without impor-tance, since the bending of a web part each time brings about the locating of a new crease line in correct posi-tion over one of the edges of the driver. The bending of the web may be done either by mechanical influence, e.g.
by means of a mechanical gripping element, or by pneumatic effect, where pressure as well as vacuum may be used.

In accordance with a preferred embodiment of the ap-paratus in accordance with the invention the device which is adapted to bend the part of the web situated between edges consists of suction heads 5 which are situated in the recessed areas in the driver 1. The suction heads are situated centrally between edges 4 of the driver situated adjoining each other and each driver side appropriately has such a number of suction heads 5 arranged in line that 115~

tlle whole width of the web is covered. Each suction head 5 comprises a flexible collar or sleeve which makes it possible to draw the material web down into the recess to such an extent that the current crease lines 3 engage with the respective edges 4.

The vacuum for the suction heads 5 is conducted to the driver 1 via connections (not shown) at the ends of the driver and supplied selectively to the suction heads as a function of the angular position of the driver. This is achieved by means of a stationary duct arranged at the end of the driver which extends around the centre axle over an angle which corresponds to the upper part of the rotation-al turn of the driver, so that the suction head; are coupl-ed to the vacuum source via connections termina~ing at theend of the driver whilst they are in their uppe:c position.
In the position shown in the Figure, for example, the suc-tion head 5' is active whilst the other suction heads are inactive. The suction head 5"' has just been inactivated ; 20 and the suction head 5" will shortly be activated on con-tinued turning of the driver.

As can be seen from the drawing, the suction heads are situated at such a depth in the areas recessed in the sides of the driver that the web which extends in a straight line between two consecutive edges 4, does not come into -~ contact with the respective suction head. According to a preferred embodiment the web is brought into contact with the suction head by a movable counter device which de-presses the web in the space between the edges 4 until the suction head can retain the web. This arrangement is of ~ a well-known type and consists of a compression roller or -~ cylinder (not shown on the drawing) which is acted upon by means of a spring in the direction towards the centre axle of the driver element 1. The device is placed appro-priately at some distance above the guide roller 6.

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It is also possible, instead o using the spring-loaded counter device, that the suction heads 5 are mov-able between a front position, wherein they project out-side the plane in which two edges 4 adjoining one another are situated, and a rear position, wherein they are drawn into the recessed area situated between the edges 4. Such a mechanism may be driven mechanically during the rotation of the driver or via the vacuum, and is to be preferred, especially in cases where the driver unit has to be fitted in a place where room is limited.

To make possible the feed of webs with different types of crease line pattern, and hence varying distance between the transverse crease lines which are utilized for a feed in register, the edges 4 may be in the form of rules which are exchangeable or adjustable in the direction to and from the centre axle of the driver, so that the dis-tance between the outer edges of the rule engaging with the crease lines 3 can be varied and adapted to the nomin-al distance between the crease lines 3 on the web which onthis occasion has to be fed. It is also possible, of course, that the driver has fixed edges and adapts the arrangement to different crease line patterns instead by a substitution of the driver.
The driver shown in the Figure has four edges, but the driver may have a different number of edges, e.g. three.
The number of edges as well as the form and length natural-ly must be adapted to the web which is to be fed.
During practical work with the apparatus of the in-vention it may happen that the distance between the crease lines on the web differs somewhat from the distance ex-pected. In such cases the apparatus according to the in-Vention allows the possibility of making a correspondingminor adjustment of the web-length between the co-operat-ing edges of the mandrel by simply adjusting the degree -:
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of vacuum to the suction cups. Thus, a stronger vacuum will deform the rim of the suction cup to a higher extent and draw the web part in question deeper down in the re-cess of the rotatable driver so that the distance for the web part running between adjacent edges in practice is lengthened. However, the vacuum applied must of course never result in such a strong force that the crease lines of the web are forced to pass the correct position over the edges, i.e. if the force caused by the vacuum is stronger than the total opposite force imparted to the web among other things by the engagement between the edge of the driver and the crease line.

In order to increase the possibility for the suction cups both to reach the web in the initial step and to draw the web down when the vacuum is applied it may also be advantageous to give the rim of each vacuum-cup a com-paratively great height so that its outermost part reaches the imaginary plane between two adjacent edges of the driver, and to give the rim a bellowlike shape in order to ensure a maximum range and flexibility.

A rotatable driver with less edges than four, prefer-ably three edges, may be favourable where the crease lines in the web are vague and indefinite and for the use to-gether with a thin and very flexible laminated web, which has a tendency to fold also in areas where no crease lines are provided.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for feeding a web provided with transverse crease lines using a rotating driver which by means of edges around its circumference engages with the crease lines, the linear distance between two crease lines for engagement with the driver being reduced by temporary bending of the web therebetween so that each of the crease lines engages with its edge.

2. A method in accordance with claim 1, in which the bending is effected by a vacuum.

3. A method in accordance with claim 2, in which the vacuum is applied during a limited part of the rotation of the driver.

4. A method in accordance with claim 2 or 3, in which the reduction of the length of the web is adjusted by vary-ing the degree of vacuum to the suction cup.

5. An apparatus for feeding of a web provided with transverse crease lines by means of a rotating driver which has axial edges distributed around its circumference for en-gagement with the crease lines, the distance between two consecutive edges on the driver is less than the correspond-ing distance between crease lines of the web, elements being arranged so as to bend the part of the web between the edges to such an extent that the crease lines coincide with the edges .

6. An apparatus in accordance with claim 5, in which the parts of the driver situated between the edges are re-cessed in relation to the plane wherein two edges adjoining each other are situated.

7. An apparatus in accordance with claim 6, in which the driver has suction heads located in the recessed areas.

8. An apparatus in accordance with claim 7, in which each of the suction heads has a flexible collar whose free end, when not acted upon, substantially touches the said plane.

9. An apparatus in accordance with claim 7, in which the suction heads are movable between a front position, wherein they project outside the said plane, and a rear posi-tion, wherein they are drawn into the recessed area situated between the edges.

10. An apparatus in accordance with claim 5, 6 or 7, which includes a movable counter device for pressing the material web into the space between the edges.

11. An apparatus in accordance with claim 5, 6 or 7, in which the edges of the driver element are formed by adjust-able rules.