A METHOD FOR BREAKING CREASES AND ERECTING A BOX BLANK

Abstract: The invention relates to a method for refolding and erecting box blanks, e.g. paper tubes. The creased or scored foldlines (6, 7, 8, 9) are refolded or "broken" to facilitate the flat box blank to be opened. A force is applied to the outside of the flat blank at the opposite side of the score lines (6, 7). The flat blank is bent by this force, the score lines break and the carton will be easier to erect. The method also provides an erecting process in direct sequence to the breaking process.

Description: A METHOD FOR BREAKING CREASES AND ERECTING A BOX BLANK The present invention concerns a procedure for opening up a box blank as defined in the preamble to Claim 1. Side-glued box blanks for use in various pack¬ ages are manufactures of cardboards, corrugated card¬ boards and plastic-coated cardboards of various thick- nesses and various qualities, and possibly also of other materials. Opening of the box blanks at the point of application is nowadays mostly accomplished using various suction grasping devices by which one side wall of the blan-k is grasped and the blank is pulled through an appropriately shaped, narrow gate so that the side walls open up to form a rectangular parallelepipedon. The problem with box blanks and with existing opening procedures is that the box blanks get warped and the grooves stiffen, particularly when the blanks have been in storage for a prolonged period, whereby the blanks fail to open up properly and tend to fold and to jam the packaging machines. Attempts have been made in prior art to reduce this problem by using for the blanks thicker and higher-quality raw materials, cardboards and equivalent, which are also more expen¬ sive at the same time, but the desired result was not achieved, since according to studies that have been made the thickness of the cardboard that is used has a minimal significance as a determinant of the force re- quired to open the box blank. The force required to open the grooves of a box blank is practically entirely dependent on the length of the groove and on its radius of curvature. The shorter and straighter the groove the easier is it to open, and vice versa. The object of the invention is to eliminate the above-described problems of prior art. It is a par¬ ticular object of the invention to disclose a novel procedure for opening side-glued box blanks, with the aid of which the box blanks are positively opened, in¬ dependent of the dimensions of the box blanks and of the straightness, or curved shape, of the blanks. Regarding the features characterizing the in¬ vention, reference is made to the Claims section. The opening procedure of the invention has relation to a box blank consisting of four side walls, two mutually opposed fold grooves between said walls which are open and two mutually opposed grooves which are closed, and of bottom flaps separated from the side walls by bottom grooves which are open. It is in- such a flat configuration that the box blanks are stored and transported -to the packaging machines to be opened up and filled. In the present application, pre-bending of a groove is understood to mean that the groove is bent in the blank-opening direction in order to reduce the for¬ ces which counteract the opening up of the blank mate- rial's fibre or equivalent structure. A groove which is open is understood to mean a groove between two side walls lying adjacent to each other in the same plane, and a groove which is closed is understood to mean a groove between two adjacent side walls which lie one upon the other. As taught by the invention, the side-glued box blank is opened up in that the grooves which are open are straightened by pre-bending them with the aid of a pressure parallelling the groove lines, from the oppo- site side of the box blank, i.e., applying pressure at a point corresponding to the groove site but on the opposite side of the blank, either at the side wall located there or at the site of another groove. The pressure pre-bending the grooves which are open is then released, and the box blank is opened up with the aid of a pressure action directed on the grooves which are closed and urging these towards each other. The move- ment causing such pressure may bear on both grooves which are closed or on one of them only, while the other groove is braced by a stationary support. Advantageously, in the procedure of the inven- tion the closed grooves on the margins of the box blank are also straightened, and this can be accomplished e.g. with appropriate rails or slots against which the closed grooves become pressed. As a rule, however, suf¬ ficient straightening of the closed grooves will take place at the same time when the grooves which are open are straightened by means of the pre-bending process. If the box blank to be opened up forms a box with rectangular cross section so that the grooves of the b+x blank which are open are not in register in the box blank but rather lie distinctly at a distance from each other on opposite sides of the box blank, then advantageously the grooves which are open are straight¬ ened and pre-bent by means of simultaneous movements in opposite directions, while at the same time the closed grooves are pressed and urged towards each other in such manner that their movement away from each other is prevented after pre-bending the open grooves. Hereby, when the pre-bending pressure on the box blank ceases, the opposed side walls will draw apart and on continued pressing of the still nearly closed grooves towards each other the box blank will open up. In another embodiment of the invention, if the opposing open grooves of the box blank lie substantial¬ ly against each other, that is, if the widths of the side walls are substantially equal, whereby the cross section of the box that will be produced is substan¬ tially square, the box blank is opened up in that the grooves which are open are pre-bent one after the other and returned to lie in the same plane with the closed grooves, whereupon the blank is opened by means of pressure acting on the closed grooves and urging them towards each other. In an embodiment of the invention, the steps of straightening, pre-bending and pressing are accom¬ plished with the aid of rows of rollers parallelling the grooves, the rows of rollers or the rollers pro- vided on them being movable for implementing the straightening, pre-bending and pressing steps, or the roller rows may be positioned to constitute a track along which the box blank travels while the rolls carry out the above-described operations which open the box blank. It is also conceivable that the straightening, pre-bending and pressing of the grooves, or any one of these operations, is effected by rails, bars or equiv¬ alent supporting surfaces running parallel to the grooves. Un an advantageous embodiment of the inven¬ tion, the members straightening, pre-bending and pres¬ sing the grooves are moved and adjusted in their later¬ al direction, whereby the distances between them are adjusted to be consistent with the dimensions of the box blanks to be processed in each instance. It is thereby possible to use, in the procedure of the inven¬ tion, one and the same opening apparatus to open up several types of box blanks of different shapes and sizes, a minimum of adjustment being needed to accom- plish this. Advantageously, one and the same opening apparatus can be used to open both such box blanks of which the grooves which are open are substantially in register and such box blanks of which the open grooves are clearly spaced from each other. In selecting the opening method to be applied one may take as criterion the distance between the open grooves and, possibly, in addition the material which is used for the box blank, the thickness thereof or any other characteristic thereof. The advantage afforded by the present inven¬ tion over the state of art is that it enables all and any side-glued box blanks to be opened, independent of their curved shape, storage time, size, material and the thickness thereof. In the following, the invention is described in detail, referring to the attached drawings, wherein Fig. 1 presents a box blank, Fig. 2 illustrates the first step in an embodiment of the opening procedure of the invention, Fig. 3 illustrates the second step in the embodiment of Fig. 2, Fig. 4 illustrates the third step in the embodiment of Fig. 2, Fig. 5 shows the opened-up blank in the embodiment of Fig. 2, Fig. 6 illustrates the first step in another embodiment of the opening procedure of the invention, Fig. 7 illustrates the second step in the embodiment of Fig. 6, Fig. 8 illustrates the third step in the embodiment of Fig. 6, Fig. 9 illustrates the fourth step in the embodiment of Fig. 6, Fig. 10 illustrates the fifth step in the embodiment of Fig. 6, and Fig. 11 shows the opened-up blank in the embodiment of Fig. 6. The side-glued box blank 1 depicted in Fig. 1 consists of a wide side wall 2, a narrow side wall 3, and underneath these, invisible in the figure, a second wide side wall and a second narrow side wall. Further ¬ more on the ends of the walls belong bottom flaps 11, which will be bent, along the bottom grooves 10, to become the bottoms of the opened-up blank. When the box blank is in its flat form as shown in Fig. 1, a groove 6 which is open belongs between the side walls 2 and 3, and a similar groove is also located on the other side of the box blank, at the same distance from the other margin of the box blank. The box blank furthermore pre¬ sents closed grooves 8 on both sides, whereby the four side walls and the interposed grooves constitute a coherent shell, which is opened up by the procedure of 5 the invention, to become a box. In the following an opening procedure accord¬ ing to the invention is described with the aid of Figs 2-5. To begin with, the box blank 1 is conducted in between the roller rows 13 so that the edges of the box 10 blank, i.e., the closed grooves 8 and 9, rest against the rotatable, and suitably shaped, rollers which, pos¬ sibly, also straighten the groove lines on the edges of the box blank. Subsequently, the roller rows 12 are caused to exert pressure (arrow A) at the locations of 15 the open grooves 6 and 7, from the side of the box blank opposite to these grooves, so that these groove lines are straightened. After this, the open grooves 6 and 7 are fur¬ ther subjected to pressure (arrow B) so that the open 20 grooves are somewhat bent, i.e., they are pre-bent in the box-opening direction. Simultaneously, the roller rows 13 are moved towards each other (arrow C) so that the closed grooves 8 and 9 stay in contact with the roller rows 13 all the time, although they come closer 25 together, owing to the box blank being bent to an arc. When the open grooves 6 and 7 have been suit¬ ably pre-bent, the effect of the roller rows 12 on the box blank 1 is removed (arrow D) , whereby the box blank, now with straight open and closed grooves, opens 30 up owing to the elasticity of the side walls 2, 3, 4 and 5, assuming a shape with parallellogram cross sec ¬ tion, as shown in Fig. 4. When thereafter the box blank 1, which has already opened up to some extent under action of the roller rows 13, is subjected to pressure 35 acting on the grooves 8 and 9, which were initially closed, urging these towards each other, the box blank opens up to become a box 16 with rectangular cross sec- tion, and the bottoms of this box can be closed in a manner known in itself in the art, and the box may be transported further to any desired application with the aid of various rollers 17. In Figs 6-11 is presented another opening pro¬ cedure conforming to the present invention, by which such a side-glued box blank can be opened up in which the grooves 6 and 7 which are open lie against each other, or nearly against each other, in the box blank. The side walls 2, 3, 4 and 5 of the box blank 1 are then substantially equal in width, and the cross sec¬ tion of the box that will be produced is substantially square. In that case the procedure just described can¬ not be applied exactly as it is because when the open grooves are located against each other they cannot be pre-bent simultaneously. Therefore, in this embodiment the box blank 1 is first pressed, Fig. 6, with the aid of elongated supporting surfaces 14 (rows of rollers as in the first embodiment may also be used) from both sides at the location of the open grooves 6 and 7 so that these groove lines are straightened. At the same time, the grooves 8 and 9 which are closed, or the mar ¬ gins of the box blank 1, are braced against elongated supporting surfaces 15, by action of which the groove lines on the margins of the box blank are likewise straightened. Hereafter, the supporting surfaces 14 are employed to bend the box blank 1 open at the sites of the open grooves 6 and 7, at first in one direction. Fig. 7, and then in the other direction. Fig. 8, thus pre-bending the open grooves. Next, Fig. 9, the open grooves 6 and 7 are returned into one plane with the closed grooves 8 and 9. As a result of the structural design of the box blank material that is being used and of the grooves, the grooves are somewhat bent in the direction causing the box blank to open up, i.e., as shown in Fig. 10 the grooves which are open draw some ¬ what apart (arrow G) as soon as the pressure acting on them is terminated. Throughout the above-mentioned pre-bending step, the supporting surfaces 15 bracing the closed grooves 8 and 9 are advantageously kept stationary. The supporting surfaces 16 are thereafter pressed towards each other (arrow F), whereby the box blank 1 opens up to become a box 19, with substantially square cross section, Fig. 11. In the foregoing the invention has been de- scribed by way of example with the aid of the enclosed drawing, while various embodiments are feasible within the scope of the inventive idea delimited by the claims.

Claims: CLAIMS 1. A procedure for opening up a side-gLued box blank, said box blank (1) consisting of four side walls (2,3,4,5) and, between these, mutually opposed grooves (6,7) which are open and mutually opposed grooves (8,9) which are closed, and of bottom flaps (11) separated from said side walls by bottom grooves (10), characterized in that - the grooves (6,7) which are open are straightened by pre-bending them with pressure, parallelling the groove lines, from the opposite side of the box blank (1), - the pressure pre-bending the open grooves is re¬ leased, and - the box blank is opened by means of pressure acting on the closed grooves (8,9) and urging them towards each other. 2. Procedure according to claim 1, character¬ ized in that the closed grooves (8,9) are straightened. 3. Procedure according to claim 1 when the box which the box blank is going to form has rectangu¬ lar cross section, characterized in that the open grooves (6,7) are straightened and pre-bent with simul¬ taneous movements in opposite directions, at the same time supporting the closed grooves (8,9) with pressure urging them towards each other. 4. Procedure according to claim 3, character ¬ ized in that with the pressure acting on the closed grooves (8,9) is prevented their movement away from each other after pre-bending the open grooves (6,7). 5. Procedure according to claim 3, when the cross section of the box which the box blank is going to form is substantially square, characterized in that the open grooves (6,7) lying substantially against each other are pre-bent in succession and are returned into one plane with the closed grooves (8,9), whereafter the box blank is opened up with pressure acting on the closed grooves and urging them towards each other. 6. Procedure according to any one of claims 1-5, characterized in that straightening, pre-bending and pressing of the grooves (6,7,8,9) is accomplished with roller rows (12,13) parallelling the grooves. 7. Procedure according to any one of claims 1-6, characterized in that straightening, pre-bending and pressing of the grooves (6,7,8,9) is accomplished with rails, bars, or equivalent elongated supporting surfaces (14,15) parallelling the grooves. 8. Procedure according to any one of claims 1-7, characterized in that in the pre-bending process the groove (6,7) which is open is pressed in the blank- opening direction in order to reduce the forces from the fibrous structure of the blank material which oppose the opening. 9. Procedure according to any one of claims 1-8, characterized in that the straightening, pre-bend¬ ing and pressing members (12,13,14,15) are moved and their positions relative to each other are adjusted in accordance with the dimensions of the box blank and the location of the grooves. 10. Procedure according to claim 9, charac ¬ terized in that simultaneous or consecutive pre-bending of the open grooves is selected in accordance with the distance of the open grooves and/or the material of the box blank.

Inventors: KOLHONEN EERO, TOIVONEN LAURI, KOLHONEN, EERO, TOIVONEN, LAURI
Applicants: KOLHONEN EERO, TOIVONEN LAURI, KOLHONEN, EERO, TOIVONEN, LAURI
Application year: 1992
Main classification: B65B43
IPC codes: B65B43