Abstract:
A liquid supply device, particularly for gluing machines, coating machines, paper moistening machines and printing machines. It includes an airtight container of collapsible design including at least one collapsible wall. The container collapses corresponding to the quantity of liquid sucked out of it by a suction pump. The collapsible container may be disposed in a rigid container with walls that support the collapsible container walls from folding over.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a liquid supply device for supplying machines with a liquid from a container wherein air is not drawn into the container. 
     Prior art includes DE 82 26 904 U1, DE 44 16 089 A1, DE 33 34 930 A1, DE 296 23 705 U1, DE 195 03 234 A1, and JP 3-246379 A. 
     Liquids, such as glue, ink and varnish, as well as organic detergents, should be kept in a liquid-tight manner so that they do not dry out and become unable to react with oxygen, their volatile constituents cannot evaporate, and no bacterial cultures can develop in them. 
     Such liquids are usually kept in containers or canisters made of polymer or metal. If the liquid is delivered from such a container using a pressure pump, air is forced into the container. As a result, the liquid can react with the oxygen in the air, volatile constituents can escape from the liquid, and the delivery rate is limited, since the containers do not withstand high air pressures from the pressure pump, or else containers made of very thick polymer material or metal are used. The use of containers with thick polymer walls or containers made of metal is expensive for their production and very expensive for their disposal (sometimes as special industrial waste) or for recycling, and the containers have a high weight. The limited pressure resistance of the containers limits the delivery pressure of the pressure pump and therefore limits the delivery rate of the liquid. This restricts the production speed of a machine being supplied with the liquid. 
     One preferred application of the invention relates to gluing machines. Glue that is to be applied to finished paper is fed from a container, for example a canister, in order to adhere paper sheets or paper webs together. Instead of paper, use can also be made of films in the form of sheets (leaves) or endless webs of polymer, metal, cork or another metal. 
     Another preferred application of the invention is in a coating machine for coating carrier material with a coating material. The carrier material is preferably paper in the form of paper sheets or paper webs. Films in the form of sheets or webs of polymer, metal, cork or another metal can also be coated. The coating material is preferably ink or varnish. 
     A further preferred application for the invention is machines or apparatus for moistening finished paper, in order to achieve a desired moisture content and to keep that content at a predetermined value or within a predetermined value range. This is done, for example, by using so-called softening liquid, which can be water, to make paper easier to crease in order that it does not tear in folding. Softening liquid may particularly be commercially available folding-aid concentrate, which is a mixture of water and additives, for example vinegar and/or washing-up liquid. 
     A further preferred application for the invention is printing machines, particularly sheet-fed printing machines and web-fed printing machines, and more particularly offset printing machines. Offset printing machines use so-called dampening solution to form ink-repellent regions on a printing plate cylinder. The dampening solution consists of water, alcohol or alcohol substitute and so-called additives. According to the invention, these liquid additives can be delivered from an airtight supply container to a dampening-solution preparation trough on the printing machine, without the additive coming into contact with air. This prevents an organic additive being infected by bacteria or fungi or being able to react with oxygen. 
     In the prior art, the liquid is forced out of the container by a pressure pump. This has the disadvantage that, at too high a delivery pressure, there is the risk that the container will burst. In addition, there is the risk that the compressed air from the pressure pump will react chemically with the liquid, or that bacteria or fungi might develop in the liquid. 
     It is also already known to suck liquid from a dimensionally stable canister with a suction pump. However, this has the disadvantages that either a vacuum that counteracts the pump suction force is formed in the dimensionally stable canister or the canister has to be vented. This leads to contact between the liquid and air or oxygen. The abovementioned disadvantages cause the liquid to dry out, or it may react with oxygen and/or bacteria or fungi may form in the liquid or in the canister. The same disadvantage as when the canister is vented also results if pressure pumps are used, because of the air delivered into the canister by the pumps. 
     SUMMARY OF THE INVENTION 
     The invention has the object of providing one possibility for delivering any desired quantities of liquid from the container while the outlay for material, the weight and the costs for the container and container disposal or recycling can be reduced, and contact between the liquid in the container and air or other gases can be avoided. 
     According to the invention, this object is achieved by a container according to the invention. At least one wall, and preferably all of the walls of the container are designed so that they can be deformed or deflected by the suction force of the suction pump which delivers the liquid and, at the same time, the container walls can be moved toward each other, without requiring the suction force of the suction pump to be significantly higher than that suction required for sucking the liquid out of an open container. 
     For this purpose, the container walls can be dimensionally unstable, e.g., the walls have either no stiffness or a stiffness that is so low that the walls can be bent easily and cannot stand upright independently without bending over, folding over or folding in on themselves. 
     According to another preferred embodiment, the walls of the container are dimensionally stable, but can be deformed plastically even by a low suction force applied by the suction pump. This means that following their plastic deformation, the container walls maintain their now deformed shape when the deformation producing forces are reduced. 
     Preferred fields of application of the invention are for gluing machines, coating machines and printing machines. In gluing machines and coating machines, the liquid is applied to a carrier in the form of finished paper or film. It is possible for the film to be metal, polymer, cork or another material. 
     According to another field of application of the invention, the liquid is a moistening liquid, for example water, for moistening finished paper in order that it can subsequently be creased more easily or can be folded in a folder without the paper tearing. 
     Furthermore, the invention can be used for offset printing machines, in order to feed liquid additive from a collapsible container to a mixing container, in which the additive is mixed with water and alcohol or an alcohol substitute in order to form dampening solution, which is fed to a printing plate cylinder to form ink-repellent regions. The dampening solution can also be fed to cylinders or rollers of the printing machine, for example paper guide rolls and cooling rolls, in order to prevent or to remove contamination, for example deposits of printing ink. 
    
    
     Other objects and features of the invention are described below, using preferred embodiments as examples and with reference to the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows schematically a liquid supply device according to the invention on a reduced scale, 
     FIG. 2 shows an enlarged detail from FIG. 1, in cross section, and 
     FIG. 3 shows the liquid supply device of FIGS. 1 and 2 in an application on a gluing machine. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows an inner container  4  which can be collapsed by the suction force of a suction pump  20 , disposed in an outer container  6  made of non-collapsible, rigid material which supports the inner container laterally 
     The collapsible container  4  has a top end with a threaded neck  8  to which the end  12  of a fluid line  14  is connectable in an airtight manner by a threaded sleeve  10 . The other end  16  of the fluid line  14  is connectable to the suction side  18  of a suction pump  20 . 
     The pressure side  22  of the suction pump  20  is connected via a further fluid line  24  to a machine  26 , of any of the types noted above, to which liquid from the container  4  can be fed by the suction pump  20 . 
     The container  4  is designed to be collapsible such that it can easily be collapsed by the subatmospheric pressure generated by the suction pump  20 , and the container collapses corresponding to the quantity of liquid sucked from it. The container offers only very low resistance to the suction force from the suction pump  20 . 
     The walls of the container  4  can be very dimensionally unstable, so that they either have no stiffness or a stiffness that is only low and is insufficient for the walls to stand upright independently without bending over, folding over or folding in on themselves. 
     According to another embodiment of the invention, although the walls of the container  4  are dimensionally stable, they can be easily deformed plastically under application of an extremely low force, which is applied by the delivery suction force of the suction pump  20 . This ability of the walls to be easily deformed plastically causes the container  4  to maintain its deformed shape when the suction force from the suction pump  20  is reduced. 
     For both described embodiments, it is advantageous to accommodate the container  4  in a dimensionally stable outer container  6 , which has side walls that support the container  4  on all its sides. The outer container  6  not only makes transport of the dimensionally unstable inner container  4  easier but also prevents the inner container being damaged. 
     In a preferred embodiment the container  4  is formed of a flexible polymer or rubber. Such containers can be produced simply and inexpensively with very thin walls, for example by cutting sections of tube from a film-like, thin polymer tube and welding both their ends together. During the welding, a line connection can be formed at one end of the tube at the same time. This connection is illustrated symbolically in FIGS. 1,  2  and  3  in the form of the neck  8 . 
     The end  12  of the suction fluid line  14  that is to be connected to the container  4  can be designed as a penetration tube  28  or may be provided with such a penetration tube  28  in order to penetrate a container closure  30  on the neck  8 . The container closure  30  can be a film welded onto the neck  8  or can be formed by the container  4  itself. The penetration tube  28  can be used without the threaded sleeve  10  or can be designed such that when the threaded sleeve  10  is screwed onto the neck  8 , it is automatically pushed through the container closure  30 . 
     Instead of a penetration tube  28 , that end of the suction fluid line  14  that is to be connected to the container  4  can have a penetration element in the form of a blade-like or needle-like tip which does not have a liquid passage opening. 
     In this case, it is necessary not only for this penetration element but also the end  12  of the suction fluid line  14  to project into the neck  8  or at least through the threaded sleeve  10  or to have a fluid connection to the latter. 
     The container  4  does not require a neck  8 . Instead, the line connection formed by the neck  8  on the container  4  can also be formed by a flat or differently shaped container wall of the container  4 , which can be the top wall, a bottom wall or a side wall of the container  4 . 
     The machine  26  can be any of the aforementioned types. 
     FIG. 3 shows, as an example, a web gluing machine  26 , in which glue from the container  4  is applied to one or both webs  32  and  34 , for example paper webs, which are bonded to each other by the glue. Gluing machines and the other types of machine on which the invention may be used are known in practice and will therefore not be described in detail. 
     The container  4  is designed such that it collapses essentially continuously, following the removal of liquid and approximately corresponding to the quantity of liquid sucked out by the suction pump  20 . 
     The collapsible container  4  preferably has the form of a flexible bag. The holding capacity of the collapsible container  4  is at least one liter (one cubic decimeter). 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.