AU6493298A

AU6493298A - Method for the separation of a plurality of at least partly superimposed, flat articles at a predetermined point

Info

Publication number: AU6493298A
Application number: AU64932/98A
Authority: AU
Inventors: Carl Conrad Maeder; Markus Scheuber
Original assignee: Ferag AG
Current assignee: Ferag AG
Priority date: 1997-04-16
Filing date: 1998-04-07
Publication date: 1998-11-11
Anticipated expiration: 2018-04-07
Also published as: CZ9903466A3; NO994999D0; IL132132A0; DE59801001D1; ES2162425T3; IL132132A; EP0975540A1; ATE202998T1; RU2203189C2; WO1998046508A1; DK0975540T3; CZ298389B6; PL336227A1; EP0975540B1; NO313822B1; CA2285981A1; AU727498B2; JP2001519750A; CA2285981C; NO994999L

Abstract

According to the invention, a static charge is produced on the surfaces of the flat objects (2) arranged on top of each other by guiding said objects (2) through a field of direct current oriented essentially vertically to their main surfaces. This charge creates electrical forces of attraction between the surfaces of the objects and these electrical forces of attraction increase mutual bonding. This effect caused by static charging of the surfaces of flat objects arranged on top of each other is reduced or prevented for at least one or two surfaces forming a predetermined separating point, by treating this surface or these surfaces in advance with an anti-static agent (3). No concentration of charge can be built up on the treated surface or any concentration of charge which does build up is compensated very quickly, so that there is no increase in bonding at the separating point or the bonding is much slighter than between the surfaces which are not part of the separating point. Consequently, the objects at the separating point can be moved against each other with less force. The inventive method is particularly suitable for opening multi-surface printed products at specific points.

Description

P1219E 17.09.99 METHOD FOR THE SEPARATION OF A PLURALITY OF AT LEAST PARTLY SUPERIMPOSED, FLAT ARTICLES AT A PREDETERMINED POINT The invention relates to a method according to the preamble of the independent claim. The method serves to separate a plurality of at least partly superimposed, flat articles at a predetermined point. The flat articles are e.g. made from paper, card board, fabric, felt or plastic. The plurality of flat articles to be separated is e.g. a 5 multipage printed product made from paper, plastic or cardboard, which is to be opened at a predetermined point. It may also be a stack or scale formation of printed products or of flat articles made from cardboard, fabric, felt or plastic and from which stack or scale formation a specific number of articles is to be removed by separation of the plurality at a predetermined point. 10 Superimposed, flat articles are frequently separated from one another by shoving a separating element, e.g. a separating wedge between the articles to be separated. The more congruent, thin and sensitive to mechanical damage the articles in question are, the more difficult it is to successfully effect a separation using a separating element. On the one hand it is difficult to aim the element precisely at a predetermined point 15 and on the other hand the risk of the separating element damaging the narrow sides or edges of the flat articles is not negligible. Therefore, superimposed, flat articles are advantageously displaced against one an other parallel to their principal surfaces, prior to an effective separation. By such P1219E 17.09.99 -2 displacement, areas of the principal surfaces of individual articles are exposed which areas are much better suited for being acted on by a mechanical separating element than the narrow side areas of the articles. CH-440339 describes a method for displacing relative to each other two directly su 5 perimposed articles within a plurality of superimposed such articles wherein a dis placement force having a component parallel to the principal surfaces of the articles is employed. In this method, there is no action on individual narrow sides or edges of the articles. For enabling the mentioned displacement to take place between two spe cific articles of the plurality of superimposed articles (predetermined separation 10 point), whilst the other articles remain substantially undisplaced with respect to one another, the adhesion between the two specific articles is reduced compared with the adhesion between the other articles by measures suitable for reducing the friction coefficient between the two specific articles. Measures for reducing the friction coefficient, e.g. include treating at least one of the 15 surfaces to be displaced relative to each other with a lubricant or smoothing it or positioning a sliding film between the articles to be displaced. Examples of lubricants are waxes, high-viscosity silicone oils or dry lubricants. Building up on the teaching of the aforementioned patent, CH-534588 describes how a stack of flexible sheets is made separable at a plurality of different, predetermined 20 points, by applying the friction coefficient reducing measures to different, predeter mined sheets in nonoverlapping areas. The stack is separated at a specific one of the predetermined separation points by directing the displacement force to the corre sponding treated area.

P1219E 17.09.99 -3 It has been found that the processes according to CH-440339 and CH-534588 give satisfactory results in many applications. However, it has been found also that in other cases the reliability with which the displacement is effected exactly in the pre determined point is not adequate, so that the method cannot be used when high de 5 mands are made. Such cases are e.g. the separation of pages of multipage printed products for the purpose of opening the product at a predetermined point. This is especially so when the individual pages of the printed products are made from a very smooth or correspondingly coated material and therefore adhere very little to one another and/or when the individual pages of the printed products are made from dif 10 ferent materials with different friction characteristics. The object of the invention is to provide a method for separating a plurality of at least partly superimposed, flat articles at a predetermined point. With the aid of the method according to the invention it is to be possible to solve separating problems in application areas where known methods are unusable and/or to attain better results 15 than possible with the known methods. This problem is solved by the method, as defined in the claims. The inventive method is based on the fact that the adhesion between superimposed, flat articles can be increased by the static charging of their surfaces. According to the inventive method, a static charge is produced on the surfaces of the superimposed, 20 flat articles, by passing the articles through an electric d.c. voltage field oriented sub stantially perpendicular to the principal surfaces of the articles. Due to the effect of the field, dipoles are oriented or charges are displaced perpendicular to the principal surfaces and positive or negative charges are concentrated on the two surfaces of each of the articles. These charges cause electric attraction forces between the sur 25 faces of superimposed such articles and therefore, increase the mutual adhesion.

P1219E 17.09.99 -4 The effect of the static charging of surfaces of superimposed, flat articles is reduced or prevented for at least one of two surfaces participating at a predetermined separa tion point, by treating said surface beforehand with an antistatic agent. Due to the limited conductivity of the antistatic agent, charges cannot concentrate on the treated 5 surface or they are very rapidly compensated. Thus, passage through the voltage field causes no adhesion increase at the separation point or at least much less adhesion increase than it causes between not treated surfaces and therefore, the treated sur faces can be moved relative to each other by a lower force than is necessary for dis placing not treated surfaces, which displacement by low force distinguishes the sepa 10 ration point. Application of a static charge for increasing the adhesion between flat articles not to be separated combined with a planned application of antistatic agent for suppressing said effect at a separation point can also be combined with the reduction of the fric tion between the flat articles to be separated by applying a lubricant, as described 15 hereinbefore as prior art. Since for such a combination advantageously the antistatic agent and the lubricant are used on the same surface areas, the two agents can be used simultaneously in the form of a mixture in a single method step. It is also possi ble to add a luminophore to the antistatic agent or to the mixture of antistatic agent and lubricant, the luminophore being useful for checking the separation at the prede 20 termined separation point with the aid of luminescence sensors. The method according to the invention is described in greater detail hereinafter in connection with the attached Figures, wherein: Fig. 1 shows a diagram of the successive steps of the inventive method; Fig. 2 shows the inventive method using the example of multipage printed products 25 to be opened at a predetermined point; P1219E 17.09.99 -5 Figs. 3 & 4 show two examples of printed products provided with a plurality of pre determined opening points. Fig. 1 shows a diagram of the successive method steps using the example of a stack 1 comprising five superimposed, flat articles 2. The stack is to be separated by dis 5 placing the two upper articles with respect to the three lower articles. Thus, the pre determined separation point is located between the upper surface of the third article and the lower surface of the fourth article within stack 1. Before or during stacking articles 2, at least one of the surfaces participating at the separation point is treated, e.g. coated with an antistatic agent 3. 10 Antistatic agents are more particularly known from the plastics industry. They are e.g. conductive particles (e.g. carbon black, carbon fibres, nickel-coated mica, steel fibres or aluminium platelets) finely distributed usually in a plastic matrix, or ionic compounds (e.g. quaternary ammonium salts), surfactants (e.g. glycol esters, glycol ethers or esters and salts of fatty acids) or hygroscopic substances (e.g. glycerol or 15 polyglycol), which are used as such or in the form of aqueous or alcoholic solutions. The treatment with the antistatic agent may comprise spraying or roller application if the agent is liquid or melted. In the case of a solid agent the treatment may comprise a direct rubbing off or rubbing off with a brush onto the surface to be treated. For applications of the inventive method to printed paper, it is also possible to mix the 20 aforementioned conductive particles into the printing ink with which the paper is printed. For this purpose, e.g. the conductive pigment Minatec @ sold by Merck in Darmstadt is suitable.

P1219E 17.09.99 -6 Through the application of such antistatic agents the surface resistance of the treated surfaces is reduced to normally 10 1 to 108 Q The surface treated with the antistatic agent 3 constitutes within the stack one of the surfaces to be displaced relative to each other. It is obviously also possible and even 5 advantageous in certain applications, to treat not only one surface of the separation point, but instead treat both surfaces participating at the separation point. The stack 1 is then exposed to a d.c. voltage field, wherein the field lines are oriented substantially perpendicular to the principal surfaces of the articles. For this purpose the stack is passed between two electrodes 10, e.g. between two plates or rods to 10 each of which a different constant potential is applied. By the effect of the field, di poles are oriented or charges are displaced within the flat articles. Between the two surfaces of an article a potential difference is built up or the surfaces of the article are statically charged (diagrammatically represented by small plus and minus signs in Fig. 1). These charges are opposed at superimposed surfaces of adjacent articles and 15 cause electric forces of attraction between the articles. At surface points where the antistatic agent acts, little or no charge can build up as a result of the increased surface conductivity, so that in such surface areas the forces of attraction between the articles are correspondingly lower. In the method diagrammatically illustrated by Fig. I the entire surface of an article 2 20 is treated with the antistatic agent and the entire stack or the entire base surface of the stack is exposed to the d.c. voltage field. This is not a condition for the inventive method. As will be shown in connection with Figs. 3 and 4, the antistatic agent may be applied to a surface only zonally. It is also possible to electrostatically charge only P1219E 17.09.99 -7 part of the stack. However, electrostatic charging is to coincide with treated surface areas wherein the charged area may be smaller than the treated area. Apparatuses for producing static charges on flat articles are known from the pa per-processing industry. They are e.g. used for preventing mutual displacement of 5 loosely superimposed paper webs or sheets. An example of such an apparatus is the ion shooter of Spengler Electronics AG, Biel-Benken (Switzerland). The voltage difference between the two electrodes 10 of such an apparatus is ap proximately 10 kV. Immediately after static charging, a displacement force (arrow 11), e.g. acting on the 10 stack surface and having a component parallel to the principal surfaces of the articles is applied to the stack 1. By this displacement force l Ithe two surfaces in the stack adhering least to one another are displaced against one another, even if the force does not act at the separation point but acts e.g. on the stack surface. By displacing two articles of the stack against one another, areas 12 of principal sur 15 faces of these articles are exposed and can be acted on with mechanical means in order to effectively separate the articles of the stack. For such an action the risk of damaging the articles is much lower than for an action on narrow sides (edges) of articles as is necessary for a separation without prior displacement. In addition, the exposed principal surfaces define the separation point in such a way that it cannot be 20 missed by a mechanical separating element. Fig. 2 diagrammatically shows as an example of an application of the inventive method the production of a multipage printed product 20, e.g. a magazine or bro- P1219E 17.09.99 -8 chure, and an opening of the printed product 20 between two predetermined pages, in order to insert a supplement. The printed product is e.g. grouped and stitched in a collecting and stitching drum through collecting prefolded sheets, as is very diagrammatically shown in the top line 5 of Fig. 2. Additionally, the printed product can also be trimmed on three sides. Dur ing the collecting a corner area 22 is treated with an antistatic agent, e.g. by spraying from a spray head 21 onto an inner page of the printed product. Following production, the closed printed product is passed between two electrodes 10, so that the pages of the product are statically charged. Immediately following 10 charging, a displacing force 11 is applied to the outside of the printed product in the corner area in which one of the inner pages is treated with the antistatic agent. Due to the force the pages between the separation point and the force application are de formed and displaced relative to the other pages. It is now possible without any risk to insert into the printed product a per se known and not shown opening element at 15 the separation point and to e.g. insert a supplement (arrow 23). Figs. 3 and 4 show multipage printed products 30 with a bound, stitched or glued spine 31, said printed products having more than one predetermined separation point. In the same way as described in the aforementioned CH-534588, said separation points are implemented by pages, which zonally carry an antistatic agent. The treated 20 areas of the different separation points are advantageously non-overlapping corner areas 32, 33 and/or edge-adjacent areas 34, 35. After charging the articles it is possi ble to open the product in a specific one of the separation points by applying a dis placement force on the outside of the product to one of the areas 32 to 35.

P1219E 17.09.99 -9 The static charging of flat articles produced by the d.c. voltage field decreases in a relatively short time. It is therefore important to have the displacement force acting immediately after charging. However, the action of the antistatic agent remains over a very long time, so that the time between the application of the agent and the 5 charging can be of any length. At any time after a first charging, charging can be repeated and the articles can be again mutually displaced in the described manner and at the same predetermined separation point.

Claims

18.09.99 -10 CLAIMS 1. Method for separating a plurality of at least partly superimposed, flat articles (2) at at least one predetermined separation point, wherein two surfaces of two arti cles (2) participating at the separation point are displaced relative to each other 5 by a displacement force (11), characterized in that the adhesion between the su perimposed, flat articles (2) is increased by static charging wherein the static charging and consequently the adhesion of surfaces participating at a separation point compared with surfaces not participating at a separation point is reduced by reducing the surface resistance such rendering the surfaces participating at a 10 separation point more easily displaceable against one another. 2. Method according to claim 1, characterized in that at least one of the surfaces participating at the separation point is at least zonally treated with an antistatic agent (3) prior to superimposing the articles (2), that the superimposed articles (2) are statically charged with the aid of a d.c. voltage field and that immediately 15 following charging the displacement force (11) is applied to the plurality of su perimposed flat articles (2) in such a way that the displacement force (11) having a component parallel to the principal surfaces of the articles acts on the separa tion point in the treated area (22) displacing the surfaces participating at the sepa ration point against one another. 20 3. Method according to claim 2, characterized in that the at least one surface par ticipating at the separation point is simultaneously treated with an antistatic agent (3) and with a lubricant and/or luminophore. P1219E 18.09.99 -11 4. Method according to one of claims 1 to 3, characterized in that the antistatic agent (3) is liquid and is sprayed onto the surface or is applied with the aid of rollers to the surface or that the antistatic agent is solid and is rubbed onto the surface to be treated. 5 5. Method according to claim 4, characterized in that the antistatic agent (3) consists at least partly of electrically conductive particles, of an ionic compound, of a sur factant or of a hygroscopic substance and that the surface treated with the anti static agent has a surface resistance of 1010 to 108 . 6. Method according to one of claims 1 to 3, characterized in that the flat articles 10 are made of printed paper and that the antistatic agent comprises conductive par ticles, which are admixed with the printing ink and are applied to the surface to be treated during printing. 7. Method according to one of claims 1 to 6, characterized in that the d.c. voltage field has a potential difference of approximately 10 kV. 15 8. Method according to one of claims 1 to 7, characterized in that the entire articles (2) are exposed to the d.c. voltage field. 9. Method according to one of claims 1 to 7, characterized in that the articles are only zonally exposed to the d.c. voltage field, the areas exposed to said field sub stantially coinciding with an area treated with the antistatic agent of at least one 20 of the surfaces participating at a separation point. P1219E 18.09.99 -12 10. Method according to one of claims I to 9, characterized in that for separation of a plurality of superimposed, flat articles (2) at a plurality of predetermined separa tion points, a plurality of surfaces are treated in non-superimposed and non-overlapping areas (32 to 35) with an antistatic agent and the displacement 5 force (11) for separation in a specific one of the plurality of separation points is directed to the treated area of one of the surfaces participating at the specific separation point. 11. Use of the method according to one of claims 1 to 10 for the predetermined opening of multipage printed products (20). 10 12. Use according to claim 11, characterized in that during production a plurality of pages of the multipage printed products (30) are treated with an antistatic agent at non-overlapping corner areas (32, 33) and/or at edge-bordering areas (34, 35). 13. Use according to claim 11, characterized in that together with the antistatic agent a luminophore is applied and that the predetermined opening is checked with the 15 aid of a luminescence sensor.