NO313822B1 - Method of separating a plurality of at least partially adjacent flat objects at a predetermined location - Google Patents

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

The invention relates to a method according to the preamble of the independent claim. The method serves to separate a number of flat objects lying at least partially on top of each other at a predetermined location. The flat objects here consist of e.g. of paper, cardboard, textile, felt or plastic. The number of flat objects to be separated is e.g. a multi-sided printed product made of paper, plastic or cardboard to be opened

a specific place, or it is a stack or a roofed formation of pressure-applied products or flat objects of cardboard, textile, felt or plastic, from which stack or roofed formation a certain number of objects must be removed by separation at a specific place.

Flat objects lying on top of each other are often separated by pushing a separating element, e.g. a separating wedge, between the objects to be separated. The more covering-like, the thinner and the more sensitive to mechanical damage the objects are, the more difficult is the separation with the help of separating elements, because on the one hand it presents difficulties to hit with the separating element a precisely predetermined place, and on the other on the other hand, there is a risk, which must not be underestimated, of damaging the narrow side or the edge of the flat object with the separating element.

For this reason, flat objects lying on top of each other are preferably first displaced parallel to each other at their main surfaces. Thus, areas in the main surface are left free from single objects; these main surface areas are significantly better suited for the introduction of a mechanical separating element than the narrow side areas.

In PS CH-440339, a method is described by which, with a displacement force that exhibits a component parallel to the main planes of the objects, in a number of flat objects lying on top of each other, two objects lying directly on top of each other are displaced, and that without affecting certain narrow sides or edges of the objects. In order to carry out the displacement in a targeted manner between the two objects determined in advance (predetermined point of separation), while the other objects remain essentially undisplaced in relation to each other, the adhesion between the two mutually displaced objects is reduced in relation to the adhesion between the other objects , so that the corresponding coefficient of friction is reduced by corresponding precautions.

As precautions for reducing the friction coefficient, it is suggested e.g. a treatment with a slip agent or a smoothing of at least one of the surfaces to be displaced among themselves, or the positioning of a sliding foil between the objects to be displaced. As a lubricant, e.g. wax, high-viscosity silicone oil or dry lubricants.

In PS CH-534588 it is described, based on the teachings of the above-mentioned patent document, how a stack of flexible sheets can be separated at several different predetermined locations, when the aforementioned precautions for reducing the coefficient of friction at different, predetermined sheets are used in areas that do not overlap. Depending on the point of attack of the displacement force, the stack can then be separated at one of the predetermined locations.

It has been shown that the method according to the two patents CH-440339 and CH-534588 certainly gives satisfactory results in many areas of application. But it has also been shown in other cases that the reliability with which the pre-determined location is really hit is not sufficient so that the method cannot be used in case of large demands. Such cases are e.g. to separate the sides of multi-sided printed products in order to open the product at a predetermined location, especially when some sides of the printed product consist of a very smooth or similar coated material so that the sides stick very little to each other, and/or when the individual sides of the printed product consist of different materials with different frictional properties.

The task of the present invention consists in providing a method for separating a number of flat objects lying at least partially on top of each other at a predetermined location. With the help of the method according to the invention, the separation process must be able to be used in areas of application where the known methods cannot be used, and/or it must be possible to achieve better results than is possible with the known methods.

This task is solved by the method as defined in the patent claims.

The method according to the invention is based on the knowledge that the adhesion between flat objects lying on top of each other can be increased by static charging of their surfaces. According to the method according to the invention, a static charge is generated on the flat objects lying on top of each other as they are passed through a DC electric field directed essentially perpendicular to the main surface of the object. Due to the effect of the field, dipoles are directed or charges are shifted across the main surface and positive or negative charges concentrate on the two surfaces of each of the objects. With these charges, electric forces of attraction are formed between the surfaces of different objects which reinforce the mutual adhesion.

The aforementioned effect of the static charging of the surface of the flat objects lying on top of each other is reduced or prevented for at least one of two surfaces which are partial at a predetermined separation point, this surface being treated in advance with an antistatic agent as follows that charge concentrations cannot form on this surface or these are quickly equalized due to the limited conductivity of the antistatic agent. Thus, there is no increase in adhesion at the point of separation or it is at least much less than between the surfaces that do not belong to a point of separation, so that the treated surfaces can be moved relative to each other with the help of less power consumption and are thus excellently suited as a point of separation.

The use of a static charge to increase the adhesion between flat objects not to be separated, combined with the targeted use of an antistatic agent to suppress said effect at a place of separation, can also be combined with the reduction of friction between the flat objects which is to be separated, by targeted application of a lubricant as described at the outset as known technique.

Since the antistatic agent and the lubricant in such a combination can advantageously be used on the same surface area, both agents can be used simultaneously, so to speak as a mixture in a single method step. In the same way, a luminophore can also be added to the antistatic agent or the mixture of antistatic agent and lubricant, with the help of which the opening at the pre-determined separation point can be checked using luminescence sensors.

The five-speed method according to the invention will be described in more detail in the following with the help of the drawings. There shows

fig. 1 a diagram of the successive steps of

the method according to the invention;

fig. 2 the method according to the invention on an example of multi-sided printed products to be opened at a specific location;

fig. 3 and 4 two examples of pressure-applied products which are

provided with a number of openings.

Fig. 1 schematically shows the successive steps of the method according to the invention on the example of a stack 1 consisting of five flat objects 2 lying on top of each other, with the top two objects to be displaced relative to the three bottom objects in order to separate the stack. The predetermined dividing point is thus located between the top surface of the third object and the bottom surface of the fourth object in stack 1.

Before or during the stacking of the objects 2 on top of each other, are treated, e.g. is coated, at least one of the surfaces participating in the separation point with an antistatic agent 3.

Antistatic agents are particularly known from the plastics industry. This concerns e.g. on conductive particles (e.g. carbon black, carbon fibres, nickel-coated mica, steel fibers or aluminum particles) that are finely divided in a matrix consisting mostly of a plastic, or on ionic compounds (e.g. quaternary ammonium salts), surfactants substances (e.g. glycol esters, glycol ethers or esters and salts from fatty acids) or hygroscopic substances (e.g. glycerol or polyglycol) which are used as such or in the form of aqueous or alcoholic solutions.

The treatment with the antistatic agent can, in the case of a liquid agent or a molten agent, be spraying or application with a roller, and in the case of a solid agent, a direct tear-off or a tear-off with a brush on the surface which must be processed. For applications of the method according to the invention on printed paper, it is also possible to mix the above-mentioned conductive particles into the printing ink with which the paper is to be printed. Suitable for this, e.g. also the leading pigment "Minatec" marketed by the company Merck in Darmstadt.

When using such antistatic agents, the surface resistance of the surfaces to be treated is usually reduced to IO<10> to IO<8> Q.

In the stack 1, the surface which is treated with the antistatic agent 3 forms one of the surfaces which must be mutually displaced. It is of course also possible, and in certain applications also advantageous, not only to treat one surface at the separation point with an antistatic agent, but both surfaces participating in the separation point.

The stack 1 is exposed to a direct voltage field whose field lines are centered essentially perpendicular to the main surfaces of the objects. For this purpose, the stack is passed between two electrodes 10 e.g. between two plates or rods, between which there is a constant potential difference. Due to the effect of the field, dipoles are centered in the flat objects or charges are displaced so that a potential difference builds up between the two surfaces of an object or a static charging of the surface, as shown schematically in fig. 1 using small plus and minus signs. These charges are opposite on overlapping surfaces of neighboring objects so that electrical attraction forces are formed between the objects.

At surface locations where the antistatic agent works, no or only very insignificant charges can build up, thanks to the increased surface conductivity, so that the force of attraction there between the objects is correspondingly smaller.

In the method which is schematically shown in fig. 1, the entire surface of an object 2 is treated with the antistatic agent and the entire stack or the entire base of the stack is exposed to the direct voltage field. This is not a condition for the method according to the invention. As shown in fig. 3 and 4, the antistatic agent can only be applied to a surface in certain areas. Furthermore, it is possible to charge only part of the stack electrostatically. Meanwhile, an electrostatic charging of the surface areas that overlap with the treated surface area is necessary, since the charged area can also be smaller than the treated area.

Devices for generating static charges on flat objects are known from the paper industry. They are used e.g. to prevent a mutual displacement of paper webs lying loosely on top of each other or sheets lying loosely on top of each other. An example of such a device is the ion shooter (Ion Shooter) from the company Spengler Electronics AG, Biel-Benken (Switzerland).

The prevailing voltage difference between the two electrodes 10 of such a device is in the order of 10kV.

Immediately after the static charging, a displacement force (arrow 11) is applied to the stack 1, which e.g. acts on the stack surface and exhibits a component parallel to the main surfaces of the objects. With the help of this displacement force 11, the two surfaces in the stack that adhere least to each other are displaced, even when the force does not attack precisely at the point of separation, but e.g. on sta-belover laten .

Due to the mutual displacement of the objects of the stack, areas 12 are released in the main surfaces of objects where the objects can be effectively separated by mechanical means. With such an attack, the risk of injury is significantly less than with an attack on the narrow sides (edges) which would be necessary for a separation without prior displacement. Furthermore, the separation point is defined so that it cannot be avoided with a mechanical separation element.

Fig. 2 shows schematically as an exemplary application of the method according to the invention the production of a multi-sided pressure-applied product 20, e.g. a magazine or a brochure, and a targeted opening of the printed product 20, e.g. to insert a voucher in a pre-determined location.

The pressure-applied product is put together, e.g. by collecting and stapling together previously folded sheets in a collection and stapling drum, as shown very schematically in the top line of fig. 2. In addition, the printed product can be trimmed on three sides. During collection, a corner area 22 is treated with an antistatic agent, e.g. by spraying it on one of the inner sides of the finished pressure-applied product from a spray head 21.

After the pressure-applied product is finished, it is passed in a closed state between two electrodes 10, whereby the individual sides of the product are statically charged. Immediately after charging, a displacing force 11 is exerted on the outer side of the pressure-applied product in the corner area where one of the inner sides is treated with the antistatic agent, whereby the sides between the parting point and the force attack are deformed and displaced towards the remaining sides. At the point of displacement, a per se known opening element (not shown) can now be pushed without risk into the pressure-applied product and provided with an attachment (arrow 23).

Fig. 3 and 4 further show multi-sided printed products 30 with a bound, stapled or glued spine 31, which printed products are provided with more than one pre-determined separation point. These separation points are, as already described in the initially mentioned patent document CH-534588, realized with the help of pages such as e.g. is provided with an antistatic agent. Here, the areas for the different separation points are preferably non-overlapping corner areas 32 and 33 and/or areas 35 and 35 which border edges. With a targeted displacement force which on the outside of the product attacks one of these areas 32 to 35, only one of the separation points is activated after a charge of the objects in a targeted manner.

The static charging of flat objects generated by the direct voltage field breaks down in a relatively short time. It is therefore important to let the displacement force work immediately after charging. However, the effect of the antistatic agent persists over a very long time so that the trid space between the application of the agent and the charging can be any, and in particular that the objects can also be pushed apart again in the described manner and at the same predetermined separation point at any time after a renewed recharge.

Claims (13)

1. Method for separating a number of flat objects (2) lying at least partially on top of each other at at least one pre-determined separation point, whereby two surfaces of two objects (2) that are part of the separation point are displaced relative to each other by means of a displacement force (11), characterized by at least one area (22) of at least one surface that participates in the separation site, is treated with an antistatic agent (3) to reduce the electrical surface resistance, that then the flat objects at least on the surfaces that do not participate in the separation site is exposed to a direct voltage field to increase the static charge, and that the displacement force (11) is then applied so that a component of the displacement force which acts parallel to the main surfaces of the objects acts on the parting point in the treated area (22), the surfaces participating in the parting points being displaced in relation to each other. 2. Method as stated in claim 1, characterized in that the treatment with the antistatic agent is carried out before the objects (2) are placed on top of each other. 3. Method as stated in claim 2, characterized in that at least one of the surfaces participating in the separation point is simultaneously treated with an antistatic agent (3) and a lubricant. 4. Method as stated in one of claims 1 to 3, characterized in that the antistatic agent (3) is liquid and is sprayed on the surface or applied by means of rollers on the surface, or that the antistatic agent is solid and is scraped off on the surface to be processed. 5. Procedure as stated in claim 4, characterized in that the antistatic agent (3) at least partially consists of electrically conductive particles, of an ionic compound, of a surface-active substance, or a hygroscopic substance, and that the surface treated with antistatic agents has a surface resistance of IO<10> to IO<8> Cl. 6. Method as specified in one of claims 1 to 3, characterized in that the flat objects consist of pressure-applied paper, and that the antistatic agent consists of conductive particles that are mixed with the printing ink and carried under the pressure application on the surface to be treated. 7. Method as specified in one of claims 1 to 6, characterized in that the direct voltage field has a potential difference in the range of 10kV. 8. Method as stated in one of claims 1 to 7, characterized in that the entire objects (2) are exposed to the direct voltage field. 9. Method as stated in one of claims 1 to 7, characterized in that the objects are only exposed to the direct voltage field in one area, whereby the areas exposed to the direct voltage field essentially overlap an area that has been treated with the antistatic agent by at least one of the surfaces involved in the separation point. 10. Method as stated in one of claims 1 to 9, characterized in that a number of flat objects (2) lying on top of each other are treated with antistatic agents to separate a number of surfaces at predetermined separation points in non-on top of each other and in non-overlapping areas (32 to 35), and that the displacement forces (11) for the different separation processes are directed towards the different treated areas. 11. Method as stated in claims 1 to 10, characterized in that the flat objects form the sides of a multi-sided pressure-applied product (20) and that this is opened purposefully by means of the separation. 12. Method as stated in claim 11, characterized in that the multi-sided pressure-applied products (30) are treated with an antistatic agent during their production on different sides of non-overlapping corner areas (32, 33) and/or on areas ( 34, 35) that adjoin an edge. 13. Method as stated in claim 11, characterized in that a luminophore is applied with the antistatic agent, and that the targeted opening is checked using a luminescence sensor.