AN ARRANGEMENT ON PACKING MACHINES

Abstract: An arrangement for the retaining of container blanks (1) in a predetermined correct position on mandrels (2) on a packing machine of the type which manufactures filled and closed packing containers from tubular container blanks and which comprises, among other things, a stepwise rotatable mandrel wheel (3) which is the bearer of mandrels distributed around the mandrel wheel which are intended to move container blanks applied to the mandrels in correct position between successive processing stations so as to achieve a bottom closure of the blanks. The arrangement comprises clamping elements (14) pressed against the mandrels in the form, for example, of a lever which is adapted so as to be pivotable in a bracket (15) at one lateral surface of the mandrel which has an upper clamping arm (14a) pressed against the mandrel and a lower manoeuvring arm (14b) rigidly connected with the clamping arm as well as a spring element (16) arranged at the top of the clamping arm (14a). The clamping element (14) and the spring element (16) can be disengaged from the mandrel through the effect of stops (17) located at one or more of the said stations which are adapted to act upon the manoeuvring arm (14b) so that the latter through a forced pivoting movement adjusts the clamping arm (14a) and the spring element (16) into a position wholly or partly disengaged from the mandrel (2).

Description: The invention relates to an apparatus for clamping a tubular container blank against a mandrel of a packing machine of the type which manufactures packing containers from said container blanks. Apparatus of these types are described in GB-A-362 705. The clamping element clamps the blank against the mandrel by the help of a lever which is pivotably journalled to the mandrel wheel. The clamping position of the clamping lever is controlled by said lever. According to another apparatus of such type as described in FR-A-2 243 079, a clamping plate is journalled at the free end of a lever which is pivotably journalled on the mandrel wheel. Both apparatus described above need complicated means for adjusting the different positions of the clamping plate and clamping lever, respectively. Containers of the so-called ridge or gable-top type have been known for a long time in packing technique. They are manufactured usually from container blanks prepared beforehand which appropriately can be provided with a creaseline pattern in order to facilitate the forming of the containers through folding of the panels representing the top and bottom to their final position. Frequently the blanks are coated with a thermoplastic material, e.g. polyethylene, which is used on the one hand to make the container liquid-tight and on the other hand to allow the sealing of the container by means of heat and pressure (so-called hot-sealing) so that it permanently retains its intended final form. The packages described above are used primarily as packages for liquid goods, e.g. milk or similar dairy products, and over the years different machines for the manufacture of the packages have been designed. A number of these machines have in common,for example, that they comprise one or more intermittently driven mandrel wheels, usually arranged in pairs, with mandrels on which the container blanks are intended to be moved between different processing stations which are located around the mandrel wheel or wheels, so as to achieve a liquid-tight bottom closure on the blanks. In order to make it possible altogether to bring about such a closure it is necessary not only that the container blanks should be applied to the mandrels in a correctly adapted position with regard to the actual crease line pattern, but also that the blanks so applied should be maintained in this position during the movement between the bottom-forming operations. This means therefore that any radial displacements, which may be caused for example by the pressing down forces which act upon the container blanks during hot-sealing, ought to be counter-acted as long as possible or preferably prevented altogether. On certain known packing machines such a position fixing of the blanks is provided with the help of so-called mandrel stops in the form of a stop dog, manually displaceable along a radial sliding groove in the mandrels and lockable in optional position, which defines the correct furnishing length for the blanks. One disadvantage of these known mandrel stops is of course that on resetting of the machine from one package size (container length) to another it is necessary individually to readjust all stop dogs ,which is very time-consuming and involves unnecessarily lengthy machine stoppages and consequently large production losses. Furthermore, mandrels provided with sliding grooves are relatively difficult to keep clean of dirt, since the latter tends to accumulate and deposit in the kind of recesses which such grooves represent. It is an objective of the present invention to facilitate the position and bias of the clamping lever by a simple construction. The invention is claimed in claim 1 and preferred embodiments are claimed in sub-claims. The features defined in the first part of claim 1 are known from GB-A-362705. According to the invention the clamping function of the clamping lever is adjustable with the help of stops at one or more of the processing stations. According to a preferred embodiment one arm of the clamping lever comprises a fishhook-shaped leafspring spring element on the free end of the clamping arm. It rests against the blank and the mandrel, respectively. The manoeuvring arm, however, comes into contact with the stop and stops, respectively, in the course of the rotation of the wheel that is during the movement from one processing station to another one. Depending on the dimension, position and configuration of the stop and of the manoeuvring arm the clamping arm can be moved away from or towards to the blank on the mandrel. The invention together with advantageous practical details of realization of the same will be explained in greater detail in the following with reference to the attached drawings on which Fig.1 shows schematically a packing machine which uses an arrangement in accordance with the invention, and Fig. 2a- 2c illustrate in greater detail the arrangement used in Fig. 1 during different states of operation. The arrangement in accordance with the invention is intended for the retaining of packing container blanks applied to mandrels during the forming and sealing of package bottoms of the type comprising a number of panels separated by means of crease lines which are folded together so that they partly overlap one another and are sealed with the help of heat and pressure (so-called hot-sealing). The arrangement is usable in particular on a packing machine of the type which is disclosed in Swedish patent no. 361857, to which reference is made. This type of packing machine is fed with (or converts a material web supplied to) tubular, flattened blanks 1 (Fig.1) which are manufactured from a flexible packing laminate which comprises a relatively rigid carrier layer of e.g. paper coated on both side with thermoplastic, liquid-tight and sealable material. The blanks are provided with a number of crease lines so as to be divided in a known manner into side wall panels as well as bottom and top wall panels. The blanks on being fed out from the magazine are raised so that they obtain a substantially square cross-sectional shape, whereafter they are conveyed in their longitudinal direction and are applied to a mandrel 2 adapted to the shape of the blanks on a mandrel wheel 3. The mandrel wheel may be single or double, and every machine may comprise one or more mandrel wheels. When the blank has been applied to a mandrel the mandrel wheel 3 is turned a step so that the bottom folding panels of the blank projecting at the end of the mandrel can be heated by means of a bottom heater 4, which, preferably with the help of hot air, heats the thermoplastic material layer of the bottom wall panels to softening temperature which is suitable for sealing. On continued stepwise movement of the mandrel wheel 3 in the first place a folding of the heated bottom wall panels takes place so that these overlap one another and form a substantially plane bottom which in subsequent processing stations is compressed with the help of a pressure device 5 and cooled, so that the panels are sealed in water-tight manner to one another. After further turning of the mandrel wheel 3 the liquid-tight blank provided with bottom can be pulled vertically downwards to a conveyor, which transports the blank further in longitudinal direction of the machine. In the said procedure the blank will pass a top pre-folder 6 which pre-folds slightly the top wall panels. Thereafter the blank is placed under a filling pipe 7 through which contents are supplied in the required quantity to the packing container from a contents vessel 8 with the help of a pump 9 . The packing container then continues in order to stop in the subsequent station where a top heater 10 of the hot air type heats the top wall panels of the packing container so that the thermoplastic layers obtain a suitable sealing temperature. The sealing of the top material of the packing container takes place with the help of the top sealer 11, whereupon the filled and closed packing containers via the dating device 12 and the feed-out conveyor 13 are discharged from the packing machine in finished condition. As pointed out previously, it is important that the container blanks 1 should be applied to the mandrels in correct position with regard to the crease line pattern facilitating the folding in of the bottom panels and be retained in this position with the greatest possible resistance against possible displacements during the movement between all the processing stations located around the mandrel wheel 3 so as to ensure the best possible bottom closure. This position fixing in accordance with the invention is achieved with the help of an arrangement which is indicated schematically on the machine shown in Fig.1 and which is illustrated in greater detail in Fig. 2a - 2c, to which reference will be made especially in the continued description. As is evident from Fig.2a, which shows the working position in connection with the actual application of the container blank 1 to the mandrel 2, the arrangement in accordance with the invention comprises a clamping element pressed against the mandrel 2 which in the present example is constituted of a lever 14 which is adapted so as to be pivotable in a bracket 15 supported on one lateral surface of the mandrel. The lever 14 has an upper clamping arm 14a loaded against the mandrel and a lower manoeuvring arm 14b rigidly connected with the clamping arm. The load against the clamping arm 14a may be achieved, for example, with the help of a spring fixed in the bracket 15 whose spring force endeavours to press the clamping arm 14a against the mandrel 2 so that the same, in the absence of an external counter-load against the manoeuvring arm 14b, rests with its upper part with a certain pressure against the mandrel 2 . The choice of load or spring in itself is in accordance with the art, but it is important according to the invention that the load chosen should be dimensioned so that the contact pressure, which the clamping arm 14 exercises on the mandrel 2 without counter-load on the manoeuvring arm 14b is sufficiently large in order safely to retain a container blank 1 applied to the mandrel 2 and clamped between the mandrel and the clamping arm, when the mandrel moves step-by-step between the processing stations around the mandrel wheel 3 and subjects the container blank 1 to the working operations required for the bottom closure. The clamping arm 14a is provided with a fishhook-shaped leaf spring element 16 whose straight part 16a rests mainly flat against, and with the help of screws or rivets is attached to, the clamping arm, whereas its top part 16b extends around the top edge of the clamping arm to rest with its curved, active surface against the mandrel 2. The curved top part 16b of the spring element is dimensioned so that it not only covers the top edge of the clamping arm but also extends a little beyond the same with its active surface when the straight part 16a rests flat against the clamping arm 14 as will be the case when, owing to a corresponding counter-load against he manoeuvring arm 14b, the clamping arm is pivoted off, or disengaged from the mandrel 2. When the counterload against the manoeuvring arm 14b ceases and the clamping arm, through the effect of the spring fixed in the bracket, is pressed against the mandrel 2, the projecting active surface of the curved top part 16b of the spring element 16 consequently will strike against the surface of the mandrel and, during continued enforced pivoting in of the clamping arm against the mandrel, successively force the free section of the straight part 16a of the spring element situated above the said screws or rivets successively to bend outwards from the clamping arm over a distance which by and large corresponds to the distance by which the non-loaded active surface of the spring element extends beyond the top edge of the clamping arm. The spring element bent out in this manner consequently will exercise a spring force directed against the mandrel with which the curved top part rests pressed against the mandrel. This means, as will be readily understood, that a certain intermediate clamping position is possible, namely when the counter-load acting upon the manoeuvring arm 14b is such that the clamping arm 14a is barely disengaged from the mandrel 2, whilst the spring element, thanks to the "overdimensioned" curved top part 16b continues to press against the mandrel 2 with a spring force caused by the enforced bending out. The abovementioned load against the manoeuvring arm 14b is achieved in accordance with the invention with the help of stops 17 co-operating with the manoeuvring arm and located at selected positions around the mandrel wheel 3 which to a greater or lesser extent prevent the free passing by of the manoeuvring arm and to a corresponding degree force the manoeuvring arm, and thereby the clamping arm, to carry out a pivoting movement against the effect of the spring fixed in the bracket each time the manoeuvring arm will pass such a stop during the stepwise movement of the mandrel 2. Such stops may be constituted, for example, of small manoeuvring wheels fixed to the machine frame, for example a bearing housing 18 for the driving shaft 19 of the mandrel wheel 3, in direct association with those stations around the mandrel wheel 3 where a certain disengagement of the clamping arrangement from the mandrel 2 may be desirable. In Figure 2a by way of example is shown such a station, that is to say the station at which the container blank 1 is applied to the mandrel 2, and at which it is desirable, therefore, that the clamping arm 14a as well as the spring element 16 should be completely disengaged from the mandrel 2. The corresponding stop or wheel 17 is positioned so, therefore, that during the actual application action a position is forced upon the manoeuvring arm 14b when it strikes against the stop 17 at the actual instant of the application of the blank,which is such that the clamping arm is moved a sufficient distance from the mandrel 2 to obtain complete disengagement also of the active surface of the spring element 16, as illustrated. Thus is made possible a free application of the container blank 1 which, in connection with the packing machine described here, is applied to the mandrel in such a position that the crease line pattern facilitating the folding in of the bottom is directly outside the free end surface of the mandrel 2. Another station, where a certain disengagement of the device from the mandrel 2 on the packing machine described above may be desirable, corresponds to the position marked II in Fig.1 which is illustrated in greater detail in Fig. 2b. At this station, as mentioned earlier, a heating of the bottom panels on the container blank 1, which can be folded in to overlap one another, takes place with the help of the bottom heater 4. The heater 4, which is movable to a bottom position against the mandrel 2, is provided with internal stops which are arranged so, that as the heater moves towards the mandrel 1 they strike against the container blank 1 and displace the same to such a position on the mandrel 2 that the said crease line pattern ends up accurately level with the top edge of the mandrel when the heater is in its bottom position. To make possible this radial position adjustment of the container blank 1 it is important that the clamping effect upon the container blank by the clamping device at this heating station should be adjusted so that the container blank 1 can be shifted relatively easily to the desired position on the mandrel 2, but at the same time the counter-force exercised by the clamping device against this axial displacement ought to be great enough to prevent a continued sliding on of the container blank 1 which might cause the crease line pattern to end up below the upper edge of the mandrel. Such an adjusted clamping effect is obtained in accordance with the invention in that the stop or wheel 17 arranged at this heating station (which corresponds to position II in Fig.1) is dimensioned or positioned so that by striking against the manoeuvring arm 14b it forces the clamping arm 14a to assume the intermediate clamping position described earlier which is shown in Fig.2b and which means that the container blank 1 on the mandrel 2 is subjected solely to the clamping effect from the spring element 16, since in this position the clamping arm 14a is completely disengaged from the container blank 1. A further station around the mandrel wheel 3 on the packing machine shown in Figure 1, where a disengagement of the clamping device in accordance with the invention from the container blank 1 is desirable, is, of course, the station at which the container blank is to be withdrawn from the mandrel 2. This station corresponds to the position in Fig.l marked III and which is shown in more detail in Fig.2c. In this position, as in the application station described previously wih reference to Fig.2a, it is desirable that the clamping device in accordance with the invention as mentioned should be wholly disengaged from the container blanks, so as to make the withdrawal of the same as simple as possible. The corresponding stop or wheel 17, therefore, is arranged so, just as in the application station, that by acting upon the manoeuvring arm 14b it forces the clamping arm 14a to such a pivoting position that both, the clamping arm 14a and the spring element 16, are out of contact with the container blank 1.

Claims: Apparatus for clamping a tubular container blank (1) against a mandrel (2) of a packing machine of the type which manufactures packing containers from said container blanks (1) and which includes a stepwise rotatable mandrel wheel (3) having said mandrels (2) distributed around it which during rotation thereof are movable between successive processing stations to provide a bottom closure on the blanks (1) applied thereto, wherein a clamping lever (14) comprising a spring element (16) is pivotably journalled on a bracket (15) at one lateral surface of the mandrel (2), said clamping lever (14) being loaded against said blank (1), characterized in that the said clamping lever (14) comprises an upper clamping arm (14a) and a lower manoeuvring arm (14b) rigidly connected to said upper clamping arm (14a), that said spring element (16) is arranged at the top of the free end of said upper clamping arm (14a) resting against the mandrel (2) in a regular position of said clamping lever (14) so that also said spring element (16) excites a spring force against the mandrel (2) caused by a spring part (16b) bent out over and beyond said upper clamping arm (14a) towards said mandrel (2) and that stops (17) arranged at one or more processing stations actuate said manoeuvring arm (14b) so as to permit at least the upper clamping arm (14a) of said clamping lever (14) to be disengaged from said blanks (1). Apparatus as claimed in claim 1, characterized in that the said stops (17) are constituted of small manoeuvring wheels fixed to a bearing (18) for the driving shaft (19) of the mandrel wheel (3). Apparatus as claimed in claim 1 or 2, characterized in that the spring element (16) is constituted of a fishhook-shaped leaf spring element whose straight part (16a) rests mainly flat against and is attached to said clamping arm (14a) whereas its top part (16b) extends around the top edge of the clamping arm (14a) so as to rest with its curved, active surface against said mandrel (2). Apparatus as claimed in claim 3, characterized in that the curved top part (16b) of said spring element (16) is dimensioned so that it not only wholly covers the top edge of the clamping arm (14a) but also extends a little beyond it with its active surface when the straight part (16a) rests flat against said clamping arm (14a).

Inventors: BRUVERIS, VILNIS, CARLSSON, LARS
Applicants: AB TETRA PAK
Application year: 1987
Main classification: B65B3
IPC codes: B65B43, B31B3, B31B1, B65B3