Abstract:
An adhesive application station comprising a device for binding stacked printed material using a free-flowing or liquefiable adhesive. The adhesive application station comprises, in the sliding surface for the printed materials, at least one outlet for the adhesive and a dosing device which is supplied with adhesive and can be closed by an actuator in a manual, mechanical, electronic and/or sensor-controlled manner. At least two separately closing supply lines for the adhesive end in a common supply channel for the dosing device, directly upstream of the dosing device, said lines each comprising an adhesive reservoir and a pump. In this way, especially a plurality of adhesives can be successively treated on the same installation without any retrofitting.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to an adhesive application station in a device for binding stacked printed products by means of a free-flowing or liquefiable adhesive, which station comprises, in the sliding surface for the printed products, at least one outlet opening for the adhesive and a dosing device which is supplied with adhesive and can be closed by an actuator in a manual, mechanical, electronic and/or sensor-controlled manner. 
         [0002]    For the production of books, periodicals, brochures and the like, printed products of all kinds are first brought together, stacked and fixed in a clamping device by means of a clasp. Then the back surface of the stack is milled flat and at the same time roughened. This allows the subsequently applied adhesive to be absorbed better and take effect better. If the back surface is insufficiently pretreated, the adhesion of the adhesive is poor and the binding quality is reduced. As a consequence of this, individual leaves come out during use or the bound printed products fall apart. However, the applied layer of adhesive must not only firmly bind in each individual page, but also be flexible enough to allow the bound printed products to be leafed through without any problem. 
         [0003]    Known adhesives are cold-setting adhesives, hot-setting adhesives or in particular hot-melt adhesives, such as thermoplastic adhesives; these are, for example, polyurethanes, polyolefins, such as polyethylene and polypropylene, ethyl vinyl acetate (EVA), polyethylene terephthalate (PET) and/or polystyrene. 
         [0004]    Generally, the stacked printed products mentioned are not only glued together on the back surface but also cased in a cover, which gives the adhesive bonding region increased strength and stability. 
         [0005]    According to the known prior art, the back of the stack is drawn over an application roller, which dips into a tray with liquid adhesive. However, when an adhesive application roller turns, not only is adhesive conveyed to the back of the stack of printed products but there is also the disadvantage that oxygen is introduced into the liquid adhesive. As a result, the quality of the adhesive can be impaired considerably. This is the case especially with adhesives that react with atmospheric moisture, for example a moisture-reactive polyurethane adhesive, in the case of which a pre-reaction with the isocyanate group takes place as a result of the infiltrating atmospheric moisture. 
         [0006]    Because, for example, dirt particles can get into the liquid adhesive when an adhesive application roller turns, the quality of the adhesive can be made to deteriorate still further. Infiltrating oxygen and/or contamination may bring about a considerable reduction in the adhering properties of adhesives. 
         [0007]    EP 1156931 B1 brings about a considerable improvement with respect to the harmful effect of atmospheric oxygen. The basic diagrams taken from this European patent, as shown by  FIGS. 1 and 2 , represent the binding region of an adhesive application head of an adhesive application station in plan view and in section. 
         [0008]      FIG. 1  shows a stack of printed products  10  on an adhesive application head  12  of an adhesive application station  14  ( FIG. 2 ). A sliding surface  16  of a nozzle block  18  of the adhesive application head  12  is penetrated by an outlet slit  20  for liquefied adhesive  52  ( FIG. 2 ), extending at right angles to the direction of advancement E of the printed products  10 , whereby an application edge is formed. The slit width s of the outlet slit  20  is around 0.1 mm-1 mm, in particular approximately 0.2 mm. This slit width s is generally predetermined, but it may also be possible for it to be set, for example in a way corresponding to U.S. Pat. No. 6,271,794 A. 
         [0009]    The sliding surface  16  is laterally delimited by a fixing stop  22  with a first guiding surface  24 , incorporating a directing aid  24 , and a holddown device  26  with a second guiding surface  28 , for a printed product  10 . The holddown device  26  can be displaced and exactly positioned in the direction of the double-headed arrow  30 , which extends parallel to the outlet slit  20 . The holddown device  26  carries a slide  32 , which can be pressed into the holddown device  26  counter to a resilient force within a narrow tolerance range t in the direction of the double-headed arrow  34 , likewise extending parallel to the outlet slit  20 . The slide  32  has a third guiding surface  36  for stacked printed products  10 , likewise with a directing aid  36   a . Both this third guiding surface  36  and the first guiding surface  24  are angled away and widen as directing aids  24   a ,  36   a  in a direction opposite the direction of introduction E for stacked printed products  10 . The narrow tolerance range t for the spring-return slide  32  is delimited by a bore  38  in the holddown device  26  and a bolt  40  projecting into this bore  38  from the slide  32 . 
         [0010]    For binding stacked printed products  10 , first the holddown device  26  is positioned with the slide  32  in a way corresponding to the minimum thickness d of the stacked printed products  10  and is set, for example with a screw. In the case of a tolerance range t of, for example, 0.5 mm for the thicknesses d of the stacked printed products  10 , the width g of the sliding surface  16  is set to the distance d and the tolerance range t, provided that the slide  32  is pressed in flush with respect to the second guiding surface  28  with maximum tolerance t. When stacked printed products  10  are introduced, the pressing in of the slide  32  takes place when said products are pushed along directing aids  24   a ,  36   a  of the first and third guiding surfaces  24 ,  36 . The adhesive application commences in a mechanical, electronic and/or sensor-controlled manner when the outlet slit  20  is reached and is ended when the printed product  10  leaves the region of the outlet slit  20 . 
         [0011]    Both the holddown device  26  and the slide  32  seal the outlet slit  20  when and where they rest on the sliding surface  16 . 
         [0012]    When the stacked printed products  10  are guided over the outlet slit  20 , they are pushed by the slide  32  onto the first lateral guiding surface  24 . The second guiding surface  28  does not act as such in the present case; the stacked printed products  10  slide along the third guiding surface  36  with the directing aid  36   a . During the binding according to  FIG. 1 , differences in terms of the thickness d of the stacked printed products  10 , both within the same stack and from stack to stack, are automatically compensated; an adhesive discharge alongside the printed products  10  cannot occur, not only avoiding loss of adhesive  52  but also avoiding the formation of unsightly strands of adhesive. 
         [0013]      FIG. 2  shows a basic diagram of an adhesive application head  12  of an adhesive application station  14  with a slit nozzle  42 , which comprises the outlet slit  20  shown in  FIG. 1  and a dosing shaft  44 , which is guided in a bore  38  of the adhesive application head  12  and has a longitudinal slit  46 . This dosing shaft extends over the length of the outlet slit  20  of the sliding surface  16 , onto which stacked printed products  10  are guided over a sloping introduction ramp  61 . 
         [0014]    Arranged underneath the dosing shaft  44 , which is rotatable in the direction of the double-headed arrow  48 , is an adhesive reservoir  50 , which is formed as a pressure chamber and is filled with a dissolved or molten adhesive  52 . Arranged in a pressure accumulator  54  is a pressure cylinder  56  with a plunger  58 , which is movable in the direction of the double-headed arrow  60  and protrudes into the adhesive reservoir  50 . A pressure equalizing system is formed as a result. A pressure in the adhesive reservoir  50  is determined according to EP 1156931 B1 by the cross-sectional ratio of the pressure cylinder  56  to the plunger  58  and the pressure in a pre-chamber  63  of the pressure accumulator  54 , this pressure lying for example in a range between 0.7 and 0.8 bar. 
         [0015]    The inventor has undertaken the object of providing an adhesive application station of the aforementioned type which not only ensures a low loss of adhesive and the introduction of a small amount of oxygen when the type of adhesive is changed over but additionally reduces the effort involved considerably. Greatly reduced downtimes increase the productivity of such an installation to a substantial extent. 
       SUMMARY OF THE INVENTION 
       [0016]    The object is achieved according to the invention by at least two separately closable supply lines for the adhesive, which each have an adhesive reservoir and a pump, opening out into a common supply channel of the dosing device, directly upstream of the dosing device. Special and further-reaching objects to be achieved by the adhesive application station are the subject of dependent patent claims. 
         [0017]    The dosing device according to the invention allows in particular that a number of adhesives can be used on the same installation without any retrofitting. 
         [0018]    The dosing device operates as a closed system, with the result that no oxygen is introduced into the adhesive. The dosing device is preferably formed as a dosing shaft with a longitudinal slit, which corresponds with the outlet slit and the supply channel. For design details, reference is made to EP 1156931 B1, which was acknowledged as prior art at the beginning. Instead of the longitudinal slit, other means, for example holes or a number of short slits formed along a surface line, may be provided. 
         [0019]    The separately closable supply lines, which lead to reservoirs with any adhesives, expediently different adhesives, have a shut-off element, for example in the form of a slide, a flap, a solenoid valve or a cock. The shut-off elements can be actuated by an actuator in a manual and/or program-controlled manner. Program-controlled shut-off elements are actuated in such a way that a shut-off element of one supply line closes before the respective shut-off element of another supply line can open, which corresponds to the function of an OR valve. 
         [0020]    According to one variant, it is also possible, for example when using more than two shut-off elements or supply lines, to arrange for opening or closing of the shut-off elements concerned to occur in such a way that two or more supply lines are open simultaneously, while the other shut-off elements remain closed or are closed. In this way, adhesive types and/or components are mixed with one another before or during application, for example two-component adhesives. Variable pressure regulating regimes also allow the dosing of volumetric flows, whereby a required ratio of the adhesive types and/or components to be mixed in relation to one another is achieved. 
         [0021]    Fitted with preference is a shut-off element which, as a result of the structural configuration, automatically has the effect that the adhesive is fed to the dosing device exclusively from one supply line. According to a first variant, this takes place by a nonreturn valve being fitted in each of the two supply lines. Such a nonreturn valve has, for example, a cylindrical inner space with frustoconical end faces tapering on both sides to a pipe, and a ball that is freely displaceable with play with respect to the cylinder jacket. Under the action of a return, this ball maintains sealing contact; when the adhesive is applied, sufficient material is allowed through between the ball and the cylinder jacket. A stop has the effect that the ball or some other closing body does not maintain sealing contact during the flow of material. According to a further variant, the shut-off element is a three-way cock, which can be changed over by a simple manual movement and closes one or the other supply line in an absolutely sealing manner. 
         [0022]    The shut-off element is advantageously formed as a compact built-in unit. The opening of the two supply lines into the supply channel can be integrated in this built-in unit. 
         [0023]    Provided that it allows a solution that it structurally satisfactory, three or even more closable supply lines may also open out into a common supply connector to the dosing device. 
         [0024]    The decisive advantage of the solution according to the invention is that an adhesive type and/or component can be changed over in an adhesive application station within a minute or less, by the active supply line being closed and the inactive supply line with the already connected new adhesive being opened. In this case, the adhesive to be replaced is automatically expelled from the supply channel, the longitudinal slit of the dosing shaft and the outlet slit. Before the stack to be bound with a new adhesive is introduced, the small amount of expelled, no longer used, adhesive is wiped away. This cleaning, performed in a matter of seconds, takes the place of prior-art cleaning work that generally takes about half an hour. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0025]    The invention is explained in more detail on the basis of exemplary embodiments that are represented in the drawing and are also the subject of dependent patent claims. 
           [0026]    In the schematic drawing: 
           [0027]      FIG. 1  is FIG. 1 of EP 115 69 31 
           [0028]      FIG. 2  is FIG. 2 of EP 115 69 31 
           [0029]      FIG. 3  shows a basic diagram, 
           [0030]      FIG. 4  shows a three-way cock in the two operating positions, 
           [0031]      FIG. 5  shows a nonreturn valve with two supply lines, 
           [0032]      FIG. 6  shows a variant of  FIG. 5 , 
           [0033]      FIG. 7  shows a nonreturn valve with three supply lines, and 
           [0034]      FIG. 8  shows a variant of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION  
       [0035]    In  FIG. 3 , the adhesive application head  12  of an adhesive application station  14  is merely indicated. The sliding surface  16  for the back of the printed products  10  ( FIG. 1 ) is interrupted in the transverse direction by an outlet slit  20  for the adhesive  52  ( FIG. 2 ). Arranged directly underneath the outlet slit  20  is the dosing shaft  44  with the longitudinal slit  46 ; here, the dosing shaft  44  is in a position in which it closes the outlet slit  20 . 
         [0036]    A first supply line  64 ′ is detachably flange-mounted on a first adhesive reservoir  62 ′ with a first adhesive  52 ′. This supply line can be closed by a first shut-off element  66 ′, formed as a solenoid valve. A first pump  68 ′ pumps the first adhesive  52 ′ in the direction of the dosing shaft  44 . 
         [0037]    A second supply line  64 ″ is detachably flange-mounted on a second reservoir  62 ″ with a second adhesive  52 ″. This supply line can be closed by a second shut-off element  66 ″, formed as a solenoid valve; a second pump  68 ″ pumps another, second adhesive  52 ″ in the direction of the dosing shaft  44 . 
         [0038]    The first and second supply lines  64 ′,  64 ″ are brought together to form a common supply channel  70 , which in the open position of the dosing shaft  44  corresponds with the longitudinal slit  46  of the latter. 
         [0039]    A microprocessor  72  controls the process, which is indicated by dashed lines. When a printed product  10  (FIG.  1 ) reaches the outlet slit  20 , the dosing shaft  44  is turned into the vertical position for the longitudinal slit  46 , the active, first or second, shut-off element  66 ′,  66 ″, formed here as a solenoid valve, is opened and at the same time the active pump  68 ″ or  68 ″ is actuated. When a printed product  10  leaves the region of the outlet slit  20 , the dosing shaft  44  is turned back in such a way that its longitudinal slit  46  lies outside the region of the outlet slit  20 ; the active pump  68 ′ or  68 ″ and/or the active shut-off element  66 ′,  66 ′ is immediately closed. 
         [0040]    If a series of printed products  10  runs through continuously, it is also possible for only the dosing shaft  44  to be actuated. The shut-off element  66 ′ or  66 ″ and the pump  68 ,  68 ″ may then be switched to continuous operation. 
         [0041]    If the left-hand side of  FIG. 3  is active and the right-hand side is inactive, a change of adhesive from  52 ′ to  52 ″ can be performed within approximately 30 seconds; the remains of the first adhesive  52 ′ are expelled by the new adhesive  52 ″ and, thanks to the small amount, can be wiped away by a manual movement, for example with a doctor blade. The adhesive application station  14  is then already ready to operate with the new adhesive  52 ″. 
         [0042]    In  FIG. 4 , a three-way cock  74  is represented in two operating positions. In the upper half of the figure, the first adhesive  52 ′ is fed to the supply channel  70 , in its lower half the second adhesive  52 ″ is fed to it. The three-way cock  74  can be actuated by an actuator manually or under the control of the processor  72  ( FIG. 3 ). The three-way cock  74  may be referred to as an OR valve. 
         [0043]    In  FIG. 5 , a nonreturn valve  76 , a second type of OR valve, is represented. The nonreturn valve  76  is formed in one piece; the introduced first and second adhesives  52 ′,  52 ″ are characterized by an arrow. The supply lines  64 ′,  64 ″ open out via screw fittings  78  into the nonreturn valve  76 . Formed upstream in a respective cylindrical cavity  80  is a tapering valve seat  82  for a ball  84 , which prevents a backflow. Both balls  84  are depicted in the closed position. If adhesive  52 ′ or  52 ″ is pumped, the valve concerned opens. The adhesive concerned, adhesive  52 ′,  52 ″, flows in a separate continuation of the supply lines  64 ′,  64 ″ to the downstream end face  86  of the nonreturn valve  76 . These separate discharges have the advantage that the return of one supply line  64 ′ into the other  64 ″ is minimal. 
         [0044]    According to the variant of  FIG. 6 , the two supply lines  64 ′ and  64 ″ are already brought together in the nonreturn valve  76 ; the common supply channel  70  emerges from the downstream end face  86  of the nonreturn valve  76 . As in  FIG. 5 , for the sake of simplicity, the stops of the ball  84  pressed away from the valve seat  82  are not depicted. 
         [0045]    In  FIG. 7 , three supply lines  64 ′,  64 ″ and  64 ′″ are brought together in a nonreturn valve  76  to form a supply channel  70  lying at the end face  86 . As in  FIGS. 5 and 6 , for the sake of simplicity, the stops of the ball  84  pressed away from the valve seat  82  are not depicted.  FIG. 7  is set out in such a way that, at the time under consideration, in each case only one of the three supply lines  64 ′,  64 ″ or  64 ′″ is open, the other two are closed. Mixing of the adhesives  52 ′,  52 ″,  52 ′″ is consequently ruled out. 
         [0046]    In a further exemplary embodiment (not represented), the opening and closing of the balls  84  according to  FIG. 7  is configured in such a way that, at the time under consideration, in each case two supply lines  64 ′ and  64 ″,  64 ′ and  64 ′″ or  64 ″ and  64 ′″ are open. The third supply line in each case, supply line  64 ′,  64 ″ or  64 ′″, is then closed (and vice versa). This mode of configuration allows mixing of two adhesive types or components, for example  52 ′ and  52 ″, whereas a third, separate adhesive  52 ′″ is fed in when the two other supply lines, for example  64 ′ and  64 ″, are closed. By means of variable pressure regulating regimes, a desired, individual volumetric flow is also set for each of the supply lines  64 ′,  64 ″ and  64 ′″ . In this way, quite apart from the exact dosing of the adhesives  52 ′,  52 ″,  52 ′″, a ratio required when mixing two adhesive types or components, for example three parts  52 ′ and one part  52 ″, is achieved at the same time. 
         [0047]      FIG. 8  shows a nonreturn valve  76 , in which two supply lines  64 ′ and  64 ″ are brought together to form a supply channel  70  lying at the end face  86 , whereas a third supply line  64 ′″ is taken independently to the end face  86 . The exemplary embodiment allows simultaneous opening/closing of the two supply lines  64 ′ and  64 ″, whereby mixing of the adhesives  52 ′ and  52 ″ is achieved. The proportionate ratio can in turn be set by means of variable pressure regulating regimes, whereby, quite apart from the exact dosing, a ratio required when mixing two adhesive types or components is achieved. In the second switching state, the supply lines  64 ′ and  64 ″ are closed, whereas the supply line  64 ′″ is open. Consequently, a third, separate adhesive  52 ′″ is fed in. 
         [0048]    In a further exemplary embodiment (not represented) according to  FIG. 8 , in each case only one of the supply lines  64 ′,  64 ″ or  64 ′″ is open, whereas the other two are closed. 
         [0049]    A hot-melt adhesive, a molten thermoplastic adhesive, is generally used as the adhesive  52 ,  52 ′,  52 ″,  52 ′″.