EP0476374A1

EP0476374A1 - An apparatus for applying a material strip to a packaging material web

Info

Publication number: EP0476374A1
Application number: EP91114395A
Authority: EP
Inventors: Roland Göransson; Jörgen Niske
Original assignee: Tetra Pak Holdings SA; Tetra Laval Holdings and Finance SA
Current assignee: Tetra Laval Holdings and Finance SA
Priority date: 1990-09-13
Filing date: 1991-08-27
Publication date: 1992-03-25
Also published as: SE9002910D0; CA2050704A1; JPH05212820A; SE466952B; SE9002910L; CN1059877A

Abstract

The disclosure relates to an apparatus for applying a material strip to a packaging material web, comprising a cutting unit (3) for cutting material strips from web-shaped strip material (8), a sealing unit (4) for sealing the severed material strips in register on a packaging material web (5), and a transfer device (18) for transferring the material strips from the cutting unit (3) to a desired position between the working device (19) of the sealing unit (4). The transfer device (18) fixedly retains the material strip during both the cutting operation and the transfer operation to the sealing unit, which makes it possible to realise an apparatus which operates at high speed and with exact precision.

Description

TECHNICAL FIELD

The present invention relates to an apparatus for applying a material strip to a packaging material web, comprising a cutting unit for cutting-off a material strip from web-shaped, stepwise advanced strip material, and a sealing unit for applying the severed material strip to the material web.

BACKGROUND ART

Packaging material webs of flexible type which comprise layers of, for example, thermoplastic and paper, are employed for the manufacture of, for instance, consumer packages for milk, juice or other beverages. Packaging containers of this type are often provided with opening arrangements which include some form of material strip, for example a tearing strip or a material strip which seals a prefabricated pouring spout. The material strips are normally applied to the packaging material web while this is still in web form, i.e. before reforming thereof into individual packaging containers filled with the desired contents. On the application of the strips to the packaging material web, extremely high demands are placed on rapidity, accuracy and register alignment, which have been difficult to satisfy because the small dimensions and slight material thickness of the strips render them difficult to handle, in particular at high application speeds.
One prior art apparatus for applying material strips to a stepwise advanced packaging material web comprises two sequentially disposed workstations, namely a first station in which each individual material strip is cut off from stepwise advanced strip material, transferred into abutment against the material and is provisionally secured thereto, for example by spot welding or gluing, and a subsequent, second station in which compression and fixed fusion (or alternatively gluing) of the material strip to the packaging material web are carried out. The employment of two sequentially disposed workstations necessitates not only the use of bulkier and more expensive equipment, but also complicates the manufacturing process proper, with less exact precision and slower workrates as a result.
Furthermore, in prior art apparatuses, the material strip is cut from a strip starting material whose width corresponds to the width of the material strip, i.e. the longitudinal direction of the material strip corresponds to the longitudinal direction of the starting material. Since the length of the finished material strip is normally between ten and fifty times greater than its width, this orientation necessitates advancement of a relatively long length of strip material prior to each cutting-off operation of an individual material strip, which further impedes the handling operation and slows down the working cycle.

OBJECTS OF THE INVENTION

One object of the present invention is to realise an apparatus for cutting and applying a material strip, the apparatus being compact and providing, in a single workstation, complete and finished strip application.
A further object of the present invention is to realise an application apparatus which operates with extreme accuracy and which ensures that the total surface of the material strip is completely sealed to the surface of the packaging material.
Yet a further object of the present invention is to realise an application apparatus which operates at high speed and with great reliability.
Still a further object of the present invention is, finally, to realise an apparatus for application of a material strip to a packaging material web, the apparatus not suffering from the drawbacks inherent in prior art, similar apparatuses.

SOLUTION

The above and other objects have been attained according to the present invention in that an apparatus of the type disclosed by way of introduction has been given the characterizing features that it comprises a transfer device which, by means of gripping members, is operative to retain the material strip and, after the cutting operation, to transfer the strip from the cutting unit to the sealing unit, and fixing devices for fixing the material strip in the correct position in the sealing unit.
Preferred embodiments of the apparatus according to the present invention have further been given the characterizing features as set forth in the appended subclaims.
Since the apparatus according to the present invention caters for both strip production and strip application in a single workstation, i.e. without intermediate displacement of the packaging material web, both rapid and dependable application of the material strip will be achieved in the correct position on the packaging material web. It will hereby be ensured not only that the material strip is placed in absolute register on the packaging material web, but also that the material strip arrives in the correct position in relation to the sealing unit, it being hereby possible to ensure that a complete sealing takes place throughout the entire surface of the material strip, which is vital for preventing contents and possible sterilization agent from adhering between the strip and the surface of the packaging material web in the further reforming of the packaging material web into individual, filled package containers.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

One preferred embodiment of the apparatus according to the present invention will now be described in greater detail hereinbelow, with particular reference to the accompanying, schematic Drawings which show only those details indispensable for an understanding of the present invention. In the accompanying Drawings:

Fig. 1 shows an apparatus according to the present invention in operation; and
Fig. 2 shows the sealing unit of the apparatus, seen from the side, Fig. 2a illustrating the sealing unit in a rest position, Fig. 2b showing the sealing unit in an intermediate position, and Fig. 2c showing the sealing unit in the operative position.

DESCRIPTION OF PREFERRED EMBODIMENT

The apparatus according to the present invention comprises three main parts fixedly secured on a common frame 1, namely a magazine 2, a cutting unit 3 and a sealing unit 4 which, in this order, are disposed along an advancement path for a packaging material web 5, the path being defined by per se known guide means (not shown).
The magazine 2 includes a shaft 6 for a reel 7 of starting strip material 8. The reel 7 is rotary by means of an electric motor (not shown) which is guided by means of a sensor device 9 in the form of guide rollers for the starting material 8 whose position indicates the need for strip advancement and controls the rotation of the reel 7 by the intermediary of electric devices (not shown). This type of sensing device for controlling material advancement is well known in the art and probably needs no detailed description in this context.
From the sensor device 9 of the magazine 2, the strip starting material 8 runs to the cutting unit 3 in which the starting material is led, by means of guide rollers and guides (not shown), progressively downwards so that it approaches the packaging material web 5 stepwise advanced on a slightly lower level. The cutting unit 3 includes a feeder device 10 which comprises two parallel arms 11 pivotal about a shaft 12 at the upper region of the cutting unit 3. By the intermediary of a drive arm 13, the arms 11 are connected to drive means, for example in the form of a cam surface or a piston and cylinder assembly. The shaft 12 extends transversely in relation to the direction of advancement of the strip starting material 8 and the distance between the two arms 11 slightly exceeds the width of the strip material 8. At the lower ends of the arms 11, there are provided two facing gripping members 14 for engagement with the longitudinal edges of the strip material 8, as will be explained in greater detail below. Adjacent the feeder device 10 of the cutting unit, and thereafter (seen in the feed direction of the strip material 8), there is a cutting device 15. The cutting device 15 comprises a cylinder 16 which extends transversely in relation to the strip material 8 and carries a knife 17 which is displaceable between two end positions a slight distance beyond each respective edge of the strip material 8. The cylinder 16 is preferably a linear cylinder which may be driven pneumatically or by other means. It is, of course, also possible to employ other types of cutting devices, such as a pivotal knife or the like. Depending upon the design of the cutting device, it may also be appropriate to provide, adjacent the cutting device, a movable jaw for stabilizing the material during the cutting operation proper. This may be designed as a conventional clamping jaw and will not, therefore, be described in greater detail in this context.
Seen in the direction of movement of the two material webs 5 and 8, the sealing unit 4 is disposed after the cutting unit 3, the sealing unit comprising an upper portion with a transfer device 18 and a lower portion with a sealing or working device 19. The transfer device 18 is of the same basic construction as the feeder device 10, i.e. it comprises two mutually parallel and mutually spaced arms 20 which are pivotally suspended about a shaft 21 extending transversely in relation to the strip material 8. Via the shaft 21, the transfer device 18 is connected to a pivotal drive arm 22 which is operative to be driven by means (not shown) eg in the form of a cam surface or a piston and cylinder assembly. The lower ends of the arms 20 each display their gripping member 23 (Fig. 2a), each one of which comprising an upper and a lower finger 24, 25 turned to face in a direction towards one another and disposed to grasp about both longitudinal edges of the strip material 8. The upper finger 24 is pivotally disposed in the arm 20 of the transfer device 18 and is manoeuvrable between an upper, open position and the lower, illustrated operative position by means of known, for example pneumatic, operating devices. On pivotal movement of the transfer device, the gripping members 23 move about the shaft 21 substantially from a position immediately after the cutting device 15 (Fig. 1) to a position immediately above the packaging material web 5 and flush with the working device 19 (Fig. 2a) of the sealing unit 4.
As has been mentioned above, the sealing unit 4 further includes the working device 19 which has two mutually registering jaws extending transversely in relation to the packaging material web 5, namely a lower sealing jaw 26 and an upper counter jaw 27. The counter jaw 27 is manoeuvrable between three positions by means of a toggle joint 28 which, by the intermediary of a drive arm 29, is connected to conventional drive means (not shown) eg a piston and cylinder assembly or a cam surface. All drive arms, i.e. the drive arm 13 for the feeder device 10, the drive arm 22 for the transfer device 18 and the drive arm 29 for the working device 19 may ideally be driven from cam surfaces on a common, electrically driven camshaft (not shown). The toggle joint 28 is of conventional type and acts on the counter jaw 27 so that this may be displaced vertically up and down, guided by guide rails 30 which run in sleeves 31 (Fig. 2) vertically disposed in the frame 1. The counter jaw 27 comprises two fixing devices 32 which, in slight spaced apart relationship, are slidably disposed in vertical holes in the counter jaw 27 and are actuated in a downward direction, i.e. towards the sealing jaw 26, with the aid of helical springs 33 or other spring means disposed in the holes.
The sealing jaw 26 constitutes a part of a plate cylinder 34 and has an upper, substantially rectangular working surface which is hydraulically manoeuvrable between a passive, lower position (Fig. 2a) and an active, upper position (Fig. 2c).
In addition to the parts shown on the Drawings, the apparatus according to the present invention further naturally includes a large number of conventional devices for driving, guiding and control of the apparatus. However, these are of well-known type and are not germane to the present invention, for which reason they are not shown or described in greater detail in this context.
The illustrated embodiment of the apparatus according to the present invention is particularly designed to apply, with uniform spacing, elongate, narrow material strips transversely in relation to the packaging material web. The material strips are intended to be included as a part in an opening arrangement for those packages or cartons which are subsequently manufactured from the packaging material web, and, in such instance, are often of longer length than the width of the packaging material web, since they are to extend, with a gripping portion, beyond a sealing edge in the finished package container. The material strips are manufactured from or include layers of a heat sealable plastic material and are parted, with the aid of the apparatus according to the invention, from the strip starting material 8 which has a width of 140 mm. Each finished material strip will then be of a length of 140 mm and its width will be determined by the length of the stepwise advancement of the strip material 8, which typically amounts to 6 mm.
When the apparatus according to the present invention is put into operation, the strip starting material 8 is thus advanced stepwise 6 mm at a time with the aid of the feeder device 10 whose arms 11 execute a pivotal movement so that the gripping members 14 are reciprocated along the advancement path of the strip material 8 and alternatingly grasp and release the edges of the strip material, respectively. When the strip material is advanced with the aid of the feeder device 10 at the same rate as that of consumption, the stepwise advancement is sensed by the sensor device 9 which ensures that the reel 7 is driven forwardly at a uniform speed so that the feeder device 10 can, at all times, advance the requisite length of strip material without, in this instance, being placed under loading by the mass of the reel 7.
On each advancement movement of the feeder device 10, 6 mm of the strip material 8 will be moved past the knife 17 which is located in its rest position at either end of the cylinder 16 and thus outside the side edge of the strip material 8. When the feeder device 10 has completed an advancement stroke, the transfer device 18 pivotal about the shaft 21 is located in a first position immediately adjacent the cutting device 15, which is illustrated in Fig. 1. When the transfer device 18 is located in this position, both of its gripping members 23 are flush with both edges of the strip starting material 8 and the fingers 24 of the gripping members 23 are operated to open position so that the edges of the strip material 8 can be inserted in between the fingers 24 and 25, whereafter the fingers 24 are activated to assume a closed position abutting against the fingers 25 such that the projecting portion of the strip material 8 is held captive by the gripping members 23 (Fig. 2a). As soon as the projecting end of the strip material 8 has been fixed with the aid of the gripping members 23 (and possibly further clamping devices for the material web have been activated), the cutting device 15 executes a cutting movement, whereat the cylinder 16 operates the knife 17 in a linear stroke transversely in relation to the strip material 8 so that a desired length of the strip material 8 is severed. The severed material strip is held with the aid of the gripping members 23 and is transferred to the correct position for being fixedly welded to the packaging material web 5 with the aid of the transfer device 18 which, by means of the drive arm 22, is pivoted counterclockwise about the shaft 21 until both of the gripping members 23 are located flush with both of the jaws 26 and 27 of the working device 19. Since the distance between both arms 20 of the transfer device 18 is slightly greater than the width of both of the jaws 26, 27, the transfer device 18 may unimpeded hold the material strip in this position, as is illustrated in Fig. 2a.
Once the severed material strip has thus been brought to the sealing position, the counter jaw 27 is activated by means of the drive arm 29 and the toggle joint 28 so that it can be displaced from the rest position illustrated in Fig. 2a a distance from the sealing jaw 26, to an intermediate position (Fig. 2b) in which both of the fixing devices 32 abut, with the aid of the force from the springs 33, against the material strip and urge this against the packaging material web 5. The fixing devices 32 now fix the material strip in the correct sealing position, and as soon as the counter jaw 27 has been brought to the intermediate position shown in Fig. 2b, the gripping members 23 can be released and the arms 20 of the transfer device 18 pivoted back to the position illustrated in Fig. 1 adjacent the cutting device 15. As soon as this has taken place, the toggle joint 28 is once again operated so that the counter jaw 27 is displaced to its active position, in which the toggle joint 28 is brought to an upper central position and the material strip and packaging material web can be urged against one another with the aid of the sealing jaw 26 which, by means of the plate cylinder 34, realises requisite compression force to ensure a satisfactory seal between the material strip and the packaging material web. The heating of the thermoplastic layer necessary for the seal preferably takes place by induction, and, to this end, the sealing jaw 26 is provided in a per se known manner with a coil for induction heating which may be placed in communication with a suitable power source. Other types of heating arrangement may also be employed, for example resistance heating or ultrasonic heating.
The design of the apparatus with a transfer device which grasps the material strip already before it is cut off from the strip starting material and conveys it to an accurately defined position in relation to the jaws 26 and 27 of the working device 19, in which position the fixing is taken over by the fixing devices 32 in the counter jaw 27, ensures that the severed material strip ends up at exactly the desired place in relation to the packaging material web 5 and the jaws 26, 27. By release of the gripping devices 23 prior to the actual sealing operation, the jaws 26 and 27 of the working device can be given a working surface which slightly exceeds the surface of the material strip abutting against the packaging material web, which makes it possible to reliably seal the entire surface to the packaging material web, whereby unsealed parts or pocket formation can be avoided. This feature is particularly desirable when the packaging material web is to be reformed into aseptic packaging containers, since it then passes through liquid sterilization agents which must not penetrate beneath the material strip.
The cutting-off of the strip material with such orientation that the width of the strip starting material corresponds to the length of the material strip further makes it possible to restrict the advancement length of the strip starting material 8, so that the apparatus can operate at very high speed, making it possible to carry out the entire operation in one station, i.e. the packaging material web 5 need only be stopped in register once for each strip application. Hereby, the apparatus according to the present invention can operate at extremely high rapidity and with exact precision.
The above-described, preferred type of gripping and fixing members and devices 23, 14 and 32 may be replaced by other devices of equivalent function, eg suction cups. Similarly, the feeder device 10 and the transfer device 18 may naturally be designed as devices linearly slidable along the strip starting material, but the illustrated embodiment has proved to function well in practice and is, therefore, preferred to other conceivable technical solutions.

Claims

An apparatus for applying a material strip to a packaging material web, comprising a cutting unit (3) for cutting off a material strip from web-shaped stepwise advanced strip starting material (8), and a sealing unit (4) for applying the severed material strip to the packaging material web (5), characterized in that it includes a transfer device (18), which, by means of gripping members (23), is operative to fixedly retain the material strip and, after the cutting operation, to transfer same from the cutting unit (3) to the sealing unit, and a fixing device (32) for fixing the material strip in the correct position in the sealing unit (4).
The apparatus as claimed in Claim 1, characterized in that the transfer device (18) is displaceable between a first position adjacent the cutting device (15) of the cutting unit (3), and a second position flush with the working device (19) of the sealing unit (4).
The apparatus as claimed in Claim 1 or 2, characterized in that the transfer device (18) is suspended on a shaft (21) transverse in relation to the packaging material web, and is pivotal between a first position adjacent the cutting device (15) and a second position in which it is tangential with the packaging material web (5).
The apparatus as claimed in one or more of the preceding Claims, characterized in that the gripping members (23) of the transfer device (18) comprise two pairs of fingers (24, 25) which are operative to grasp about both longitudinal edges of the web-shaped strip material (8).
The apparatus as claimed in one or more of the preceding Claims, characterized in that the fixing device (32) of the sealing unit (4) is disposed between the gripping members (23) of the transfer device (18) when the transfer device is located flush with the working device (19) of the sealing unit.
The apparatus as claimed in one or more of the preceding Claims, characterized in that the working device (19) of the sealing unit (4) consists of a sealing jaw (26) and a counter jaw (27), the fixing devices (32) being disposed in the counter jaw (27) and spring-biased in a direction towards the sealing jaw (26).
The apparatus as claimed in Claim 6, characterized in that the counter jaw (27) and the sealing jaw (26) are, in relation to one another, displaceable between three positions, namely a rest position in mutual spaced apart relationship, an intermediate position in which the counter jaw (27) has been displaced such that the fixing devices (32) have been brought into abutment against the material strip, and a working position in which the sealing jaw (26) is brought into abutment against the counter jaw (27).
The apparatus as claimed in Claim 6 or 7, characterized in that the counter jaw (27) is connected to the frame (1) of the apparatus by the intermediary of a toggle joint construction (28) which is connected to a prime mover.
The apparatus as claimed in Claim 6, 7 or 8, characterized in that the sealing jaw (26) is hydraulically operable between an active and a passive position.
The apparatus as claimed in one or more of the preceding Claims, characterized in that the cutting unit (3) is provided with feeder devices (10) for stepwise advancement of the material web (8) in a direction towards the cutting device (15).