A METHOD OF WRAPPING ARTICLES ARRANGED ON TRAYS IN STRETCH FILM AND A MACHINE FOR PERFORMING THE METHOD

Abstract: A method and a machine for wrapping articles arranged in a group (3) in a tray (2) in stretch film (12). According to the method at least one strand of glue (38) is applied on opposite walls of the tray (2), whereupon a piece of stretch film (12) is extended over the group of articles (3) and the tray with the articles thereon is assembled with the stretch film in a manner ensuring that the film encloses the grouped articles. Two opposite end portions of the length of stretch film (12) are thereafter secured in position against the tray and gripping means (13, 14) release their grip on the outermost part of said film end portions. The latter are thereafter pressed against the strands of glue to attach the stretch film to the tray. The machine includes an elevating table (1) with manipulating members (13, 14) and glue-applicators (8) on either side of the elevating table. The manipulating members (13, 14) are arranged to move towards and away from one another. One manipulating member (13) is arranged to hold the stretch film (12) with the aid of clamping jaws and pull it over the grouped articles (3). The opposite manipulating member (14) is likewise equipped with clamping jaws (29, 31) serving to hold the stretch film (12) on the opposite side of the grouped articles (3) while the film is being stretched about the latter, and also with severing means (39) cutting off the required length of film. The elevating table (1) is arranged to raise the tray (2) with the group of articles (3) thereon against the stretch film (12) while at the same time the manipulating members (13, 14) are moved towards the tray and enclose the group of articles in stretch film, and with the aid of the clamping jaws (29, 33) press the film ends against the strands of glue (38) on the walls of the tray.

Description: A Method of Wrapping Articles Arranged on Trays in Stretch Film and a Machine for Performing the Method The subject invention concerns a method of u/rapping articles arranged in a group in a tray in stretch film. According to the method at least one strand of glue is applied to each one of tuio opposite malls of the tray, u/hereupon gripping means extend a length of stretch film over the group of articles and the tray u/ith the group of articles thereon is assembled uith the stretch film in a manner ensuring that the film encloses the group of articles and is pressed against the parts of the tray inhere the glue is applied. In packaging articles in a tray of cardboard or corrugated paperboard either shrink film or stretch film is used as a rule. Shrink film is comparatively inexpen¬ sive but requires investments in shrink tunnels and energy for operating them. Wrapping in stretch film requires no shrink tunnal but this type of film is considerably more expensive than shrink film. This makes it desirable, when stretch film is used, to minimize as far as possible the amount of film required to form the package. Obviously it mould also be advantageous if it were possible to reduce the space required for the wrapping line of the machine as u/ell as the investment costs therefor. The method in accordance u/ith the subject invention has for its purpose to allou. articles, arranged in a group in a tray, to be wrapped in stretch film, using a minimum amount of the film. The method is realized u/ith the use of comparatively feu/ means, uiith the result that the u/rapping line requires very little space. The method in accordance u/ith the invention is charac¬ terised in that tuo opposite marginal portions of the lengt of stretch film are pressed against the tray, that said OlvϊF gripping means thereafter release their grip on the outer¬ most parts of said marginal portions of the film, and that said marginal film portions are thereafter pressed against said strands of glue for adhesion of the stretch film to the tray. The invention likewise comprises a machine for per¬ forming the method. The machine includes an elevating table uith conveying means thereon for advancing trays u/ith groups of articles thereon up to and away from glue spsay nozzles which are positioned on either side of the elevating table for the purpose of applying at least one strand of glue on tiuo opposite walls of the tray. The machine in accordance uith the invention is characterised by the provision of tu/o manipulating members which are arranged to move towards and away from one another. The first manipulating member is equipped with a first pair of clamping jaws and is arranged to grip the stretch film with the aid of said pair of jaws and upon its movement in the direction away from the second manipulating member to pull the stretch film over the group of articles. The second manipulating member is likewise equipped with a pair of clamping jaws serving to hold the stretch film on that side of the group of articles that is opposite the first pair of clamping jaws, hile the film is being tensioned about said group of articles, and further with severing means to cut the required length of film, as well as with retainer means to hold the forwards end of the stretch film which is intended to be used for the following wrapping operation. The elevating table is ar- ranged to raise the tray with the group of articles thereon upwards against the stretch film. The manipula¬ ting members, while being moved simultaneously from opposite directions inwards towards the tray wrap the group of articles in the stretch film and with the aid of their clamping jaws they press the film ends against the strands of glue for adhesion of the stretch film to the tray. One embodiment of the invention will be described in closer detail in the following u/ith reference to the accompanying drawings, wherein Fig. 1 is a schematic view of the machine designed to perform the method in accordance with the invention, Fig. 2 illustrates one part of this machine in a lateral view, and Figs. 3-6 show other parts of the machine in four different positions illustrating different operational phases of the method in accordance with the invention. The packaging machine illustrated in Fig. 1 is provided with an elevating table 1 onto which trays 2 with a group of articles 3 thereon are advanced by a conveyer belt (not shown). The elevating table 1 is provided with a drive mechanism comprising a motor 4, a transmission belt 5 and drive belts 6 by means of which the trays may be transferred from the conveyor belt onto the elevating table 1 into contact with a sensing means 7 serving to stop the tray displacing movement when the table assumes its lower position shown in Fig. 1. On either side of the elevating table 1 are positioned glue-applicators (glue spray nozzles) 8. The tray 2 is arranged to move past the glue applicators before it reaches the sensing means.7. Raising and lowering of the elevating table 1 to or from an upper level is effected by means of a piston-and-cylinder unit 9. Two control guides 10 are provided for guidance vertically. On the upper level of elevation of the elevating table 1 are provided a roller conveyor (not shown), onto which the finished trays are discharged, and a supply roll 11 holding stretch film 12. Two manipulating members 13 and 14 are provided at the upper level of elevation to handle the stretch film 12. The manipulating members are arranged to be moved towards and away from one another, these movements being effected by a motor 15 which is connected to a drive shaft 17 via a transmission belt 16. The drive shaft 17 supports two cog belts 18 travelling about two tensioniπg rolls 19. The drive shaft 17 and the tβnsioning rolls 19 are arranged in parallel and in the same horizontal plane. The mani- pulating members 13, 14 are mounted for sliding motion alon horizontal guides 20, the first one 13 of the manipulating members being connected to the upper belt parts of the cog belts 18 by means of a clamping joint 21 while the second manipulating member 14 is connected to the lower belt parts of the cog belts 18 by means of a similar clamping joint 21. Upon operation of the motor 15 the two manipulating members therefore are moved at the same speed towards or away from one another along the guides 20, depending on the motion of the motor. The stretch film 12 extends from the storage roll 11 via a deflector roll 22 to a retainer element 23 provided on the right-hand manipulating member 14 as seen in Fig. 1. The retainer element 23 consists of a piston-and-cylinder unit 24 supporting at one end a clamping shoe 25 serving as a back-up means 26. The latter is provided with a ruler 27 projecting horizontally towards the left-hand mani¬ pulating member 13. The manipulating member 14 is provided with a clamping jaw 29 which is pivotally mounted on a pin 28 on the upper face of the web of stretch film 12, and with a similar clamping jaw 31 which is pivotally mounted on a pin 30 on the lower face of the film 12. The two clamping jaws 29, 31 are operated by piston-and-cylinder units 32 so as to perfor a movement along a curve having a comparatively large radius The left-hand manipulating member 13 as seen in Fig. 1 is also provided with clamping jaws 33, 34, one of which is pivotally mounted on a pin 35 on the upper face of the stretch film 12, the other one being similarly pivotally mounted on a pin 36 on the lower face of the film web. These two clamping jaws are operated by piston- -and-cylinder units 37 having a shorter stroke length than do units 32 operating the right-hand manipulating member jaws. In addition, the distance between the pivot pins 35 36 and the clamping jaws 33, 34 is smaller than the distance between the pivot pins 28, 30 and the clamping jaws 29, 31 of the right-hand manipulating member 14. Consequently, the two clamping jaws 33, 34 are able to per form a pivotal movement along a curve having a compara- tively small radius. The machine operates in the following manner. A tray 2 of corrugated paperboard supporting articles 3 arranged in a group thereon (see Fig. 1 ) is transported from the conveyor belt onto the elevating table 1 which is positioned at the lower level of elevation. In this positi the glue spray nozzles 8 apply glue onto each one of the long malls of the tray, for instance as is shown at 38 representing two horizontal and parallel strands of glue. Alternatively, the glue may cover the entire tray wall. While the tray 2 is being transferred onto the eleva¬ ting table 1 the two manipulating members 13, 14 are moved towards one another by the motor 15, as shown in Fig. 1. During this movement, the clamping shoe 25 of the retainer element 23 abuts against the back-up means 26, a piece of the stretch film 12 projecting between said last-mentioned shoe and back-up means while supported by the ruler 27. The two clamping jaws 29, 31 open sufficiently far to allow the two clamping jaws 33, 34 mounted on the manipulating member 13 to reach in between the two first-mentioned clamping jaws, gripping the ruler 27, as shown in Fig. 3 and entraining the film end away from the ruler 27, OMFI The retainer element 23 is lifted off the back-up means 26, whereupon the two manipulating members 13, 14 may be moved apart by the motor 15 and the cog belts 18, whereby a length L.. of the film (see Fig. 4) is pulled out between the two manipulating members. The clamping jaw pair 29, 31 thereafter grips the film 12 and the two manipulating members 13, 14 are moved a further distance apart, 2 x L„, while tensioning the film in the lengthwise direction thereof. The clamping jaw 29 is provided with a severing means 39 which cuts off the film as the clamping jaws 29 and 31 are moved into contact with one another. At the same time the elevating table 1 isready to be lifted upwards between the guides 20 and the cog belts 18 to the upper level of elevation. Concurrently with the lifting of the elevating table 1 with the tray 2 and the articles 3 thereon against the stretch film 12 the two manipulating members 13, 14 move closer towards one another until the clamping jaws 29 and 33 abut against the longer walls of the tray (see Fig. 5). The film is still kept tensioned. The two clamping jaws* 29 and 33 are provided with pressure pads 40 urging the stretch film 12 against the upper one of the horizontal glue strands 38 (alternatively, against the upper portion of the tray wall) on either side of the tray 2. During the subsequent phase the two lower clamping jaws 31 and 34 are actuated to release their grip. The stretch film ends thus are released, the elevating table 1 is raised, and the stretch film ends then move into position against the walls of the tray and are pressed by t pressure pads 40 against the lower glue strand 38 (alter- natively, the lower portion of the tray wall) on either side of the tray 2. The latter is now ready to be trans¬ ferred by the drive belts 6 onto the roller conveyor. Befor this transfer takes place the manipulating members 13, 14 are again moved slightly apart in order not to prevent tha tray movement. When the tray has been removed from the elevating table 1 the latter is again lowered by the piston-and-cylinder unit 9 to the lower level of elevation while at the same time the manipulating members 13, 14 are returned to the position illustrated in Fig. 1. Since the stretch film is still retained by the retainer element 23 it is entrained in this movement and the machine is ready to perform the next operating cycle. The pneumatic lines incorporated in the machine are not illustrated in the drawing figures in order not to unnecessarily clutter the latter. The technique and mechanismsrequired to guide and control packages as outlined above are well known in the art and therefore need not either be described herein. With the aid of the machine defined in the afore- -going the method of wrapping articles in stretch film may be performed in a rational manner. Because the stretch film, having been extended across the articles, is applied and secured to two opposite walls of the tray 2 and not, as is the case when using prior-art technique, pulled in underneath the bottom face of the tray and secured thereto or, as is often the case, even wrapped about the entire package, each package uses considerably less of the expen- sive stretch film material. In addition, the smaller amount of wrapping material also has the advantage of making it easier to open the package as the latter need no longer be lifted to loosen the film off the tray. Further¬ more, because the wrapping operation is carried out on a short vertical path through the machine, the latter may be designed as a compact unit, requiring comparatively little space. The method in accordance with the invention is not limited to being practically realized in the machine described above but other means are possible to perform the method in accordance with the invention.

Claims: Claims 1. A method of wrapping articles (3) arranged in a group in a tray (2) in stretch film (12) by applying at least one strand (38) of glue to each one of two oppo- site walls of the tray, extending a length of stretch film (12) over the group of articles with the aid of gripping means (13, 14) and assembling the tray (2) with the group of articles (3) thereon with the stretch film in a manner ensuring that the film encloses the group of articles (3) and is pressed against the parts of the tray (2) where the glue is applied, c h a r a c t e r i s e d i n t h a t two opposite marginal portions of the length of stretch film (12) are initially pressed against the tray (2), that said gripping means (13, 14) thereafter release their grip on the outermost parts of said marginal portion of the film, and that said marginal film portions are thereafter pressed against said strands (38) of glue for adhesion of the stretch film (12) to the tray (2). 2. A method as claimed in claim 1, c h a r a c t e r i s e d b applying two horizontal strands (38) of glue on each one of said two opposite walls of the tray (2), one strand above the other, said opposite marginal portion of said stretch film (12) being pressed against said strands, initially an inner part of each marginal edge portion against the upper one of the strands of glue and thereafter the outermost part of each marginal film portion against the lower one of said strands of glue for adhesion of said stretch film (12) to the tray (2). 3. A machine for performing the method of wrapping articles (3) arranged in a group in a tray (2) in stretch film (12) as claimed in claim 1, said machine comprising an elevating table (1) with conveying means (4, 5, 6) thereon for advancing tr_ays (2) with groups of articles (3) thereon up to and away from glue spray nozzles (β), said nozzles positioned on either side of the elevating table (l) for the purpose of applying at least one strand (38) of glue on two opposite walls of the tray, c h a r a c t e r i s e d b y two manipulating members (13, 14) which are arranged to move towards and away from one another, the first one (13) of said mani¬ pulating members being equipped with a first pair of clamping jaws (33, 34) and arranged to grip the stretch film (12) with the aid of said pair of jaws and upon its mo ment in the direction away from the second manipulating member (14) to pull the stretch film (12) over the group of articles (3), and the second one (14) of said manipula¬ ting members likewise being equipped with a pair of clamping jaws (29, 31 ) serving to hold the stretch film (12) on that side of the group of articles (3) that is opposite the first pair of clamping jaws (33, 34) while th film is being stretched about said group of articles, and further with severing means (39) to cut the required lengt of film, as well as with retainer means (23,26) to hold th forwards end of the stretch film (12) which is intended to be used for the following wrapping operation, and in that said elevating table (l) is arranged to raise the tray (2) with the group of articles (3) thereon upwards against the stretch film (12) and in that said manipulating members (13, 14) are arranged, while being moved simultaneously from opposite directions inwards towards the tray (2) to wrap the group of articles (3) in the stretch film (12) and with the aid of their clamping jaws (29 and 33) press the film ends against the strands (38) of glue for adhesion of the stretch film (12) to the tray (2). 4. A machine as claimed in claim 3, c h a r a c t e ¬ r i s e d i n t h a t one of the clamping jaws (29, 33) of each one of the manipulating members (13, 14) is provided with a pressure pad (40) pressing said stretch film (12) against the tray (2) in the area of the strand (38) of glue. 5. A machine as claimed in claim 3, c h a r a c t e r i s e d i n t h a t the severing means (39) of the second manipulating member (14) is mounted on one of the clamping jaws (29, 31 ) of this manipulating member and arranged to cut the stretch film (12) while the clamping jaws are grasping the latter.

Inventors: STENBERG FOLKE G A, STENBERG FOLKE G.A.
Applicants: IWEMA PACK AB, AB IWEMA PACK
Application year: 1982
Main classification: B65B11
IPC codes: B65B11, B65B51