Abstract:
Apparatus for applying fluids such as adhesive, in particular hot-melt glue, onto a substrate that is movable relative to the apparatus. The apparatus includes a basic body ( 12 ) and an applicator valve ( 22 ) for selective interruption or release of the stream of fluid. The basic body ( 12 ) is connectable to a fluid source and includes a slit-shaped nozzle opening ( 54 ) that communicates with a distribution channel ( 14 ), and a piston ( 16 ) that is movably situated in the distribution channel ( 14 ), by means of which the length of the distribution channel ( 14 ) which may be supplied with fluid is variable. The nozzle opening ( 54 ) communicates with the distribution channel ( 14 ) by means of a plurality of output channels ( 18 ) spaced at a distance from each other.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an apparatus for applying fluids such as adhesive, in particular hot-melt glue, onto a substrate that is movable relative to the apparatus. 
       BACKGROUND 
       [0002]    Apparatuses of this sort are frequently also referred to as application heads, and are employed for example when foil or film-type substrates such as labels are to be coated extensively with liquid adhesive, for example hot-melt glue. Normally the flowable adhesive is kept in reserve in a fluid source such as a melting unit. This fluid source is connected to a basic body of the apparatus through a hose connection. Flowable adhesive is carried by a means of conveyance through corresponding holes into the apparatus and on through a distribution channel, and passes through a valve body of an applicator valve. The distribution channel communicates with a slit-shaped nozzle opening, from which the adhesive is dispensed and applied onto a substrate. Since the substrate is movable relative to the apparatus, adhesive is applied extensively to the substrate. Normally the nozzle opening is designed as an elongated slit. The length of the effective section of the slit can be adjusted by a piston that is movably situated in the distribution channel. Such an apparatus is known, for example, from DE 299 08 150. 
         [0003]    When coating labels which are to be applied, for example, to bottles, the nozzle opening is normally in a vertical orientation; that is, the slit-shaped discharge opening runs essentially vertically. This can result in the occurrence of an unwanted downward flow component of the fluid in the longitudinal direction of the slit-shaped discharge opening, due to gravity. When the apparatus is stopped for an extended time, a subsequent dripping continues to be disadvantageously perceptible, due to the fact that surplus adhesive runs down the nozzle opening and in time hardens unchecked. In consequence, before each new start-up of the apparatus the adhesive that has run down must be laboriously removed in order to guarantee a uniform application pattern in the coming application. 
         [0004]    In those uses in which the application pattern has a plurality of spaced apart strips, application apparatuses are regularly employed with a nozzle arrangement which uses nozzle plates that have a plurality of spaced cutouts, so that within the nozzle arrangement spaced, slit-shaped discharge openings occur through which the adhesive is dispensed in strips and applied to the substrate. To change the application width or pattern, the nozzle plate is uninstalled and a new nozzle plate with a different geometry is inserted into the nozzle arrangement. This process is relatively expensive and complicated. The same is true in the event that the application width must be changed. 
         [0005]    The object of the present invention is to improve and to specify an apparatus in which influences of gravity on the flow in the slit-shaped nozzle opening are reduced. Furthermore, according to another aspect the object of the invention is to provide an apparatus that avoids disadvantageous influencing of the application pattern, in particular when the discharge opening is situated vertically, to minimize running down of the adhesive when the apparatus is stopped. According to another sub-aspect, the object is to specify an apparatus in which the shape of the discharge opening, in particular the width of the application pattern, can be modified as simply as possible. 
       SUMMARY 
       [0006]    The invention solves the problem in the case of an apparatus of the type defined above by having the nozzle opening communicate with the distribution channel by means of a plurality of output channels which are spaced at a distance from each other. 
         [0007]    Because of the large number of output channels spaced at a distance from each other, together with the movable piston, it is possible in a simple way to modify the application pattern, in particular the width of the application. At the same time it is possible to prevent what occurs in the existing art, that adhesive which is in the slit between the nozzle opening and distribution channel can flow in the apparatus due to influences of gravity in such a way that the application pattern is influenced disadvantageously, in particular that it can run down at the nozzle opening while the apparatus is stopped, in particular when the apparatus is situated vertically. Because the slit is segmented between the nozzle opening and distribution channel by the output channels, flow components in the direction of the longitudinal direction of the slit-shaped discharge channel can be largely prevented or reduced. This results in uniform application. 
         [0008]    It is especially advantageous that the fluid stream through the output channels is optionally releasable or interruptible with the help of the piston. It is possible to select by the position of the piston which of the output channels have adhesive flowing through them. Because the piston has a section which forms a narrow annular gap between its outer circumferential surface and the inner surface of the distribution channel, the section of the distribution channel occupied by the piston is sealed off, so that no fluid can penetrate into this section. As a consequence, output channels which are located in the section of the distribution channel sealed off by the piston can no longer have fluid flowing through them, the result of which is that there is also no fluid flowing from the nozzle opening in this section. The width of the application surface is variable in steps by the number of outlet channels through which fluid flows. The number of output channels through which fluid flows is determined by the position of the piston in the distribution channel. The output channels can be characterized as follows by the sealing effect of the end of the piston in contact with the fluid, as described above: depending on the position of the piston in the distribution channel, they are either in front of or behind the end of the piston that is in contact with the fluid—viewed in the direction of flow of the fluid. Output channels that are located in front of the end of the piston have fluid flowing through them, while output channels that are located behind the end of the piston are cut off from the supply of fluid. As a direct result of this connection, the position of the piston in the distribution channel also determines the width of the application surface. 
         [0009]    A preferred embodiment proposes that the output channels and the nozzle opening be formed in a nozzle arrangement that is separable from the basic body. This is advantageous from the perspective of production technology, since it creates the possibility of realizing design features that are needed to produce the desired application pattern of the adhesive in a simple way. Examples of such design features could be projections for tear-off edges or recesses for a locally increased provision of adhesive, as described in DE 20 308 257. In addition, it is conceivable to use other materials for the nozzle arrangement than for the basic body, which are better suited for providing the design features named above. 
         [0010]    A preferred embodiment of the invention provides that the nozzle arrangement be made up of a first sub-block and a second sub-block, which are detachably connectable with each other and with the basic body. Dividing the nozzle arrangement into two sub-blocks increases the accessibility of both the distribution channel and the output channels, so that the latter can be cleaned and freed of hardened adhesive residues in a simple way. 
         [0011]    The invention is advantageously further refined by having the output channels formed by depressions on the corresponding surface of only one of the sub-blocks. The advantage from the perspective of production technology is that only one sub-block has to be machined, so that the time and cost of manufacturing can be reduced. Another advantage is that only one sub-block has to be exchanged when the application makes it necessary to use output channels with different geometric properties. 
         [0012]    According to a preferred embodiment of the invention, the output channels have a cross section that grows larger toward the nozzle opening. The enlargement of the cross section has the advantage that with appropriate dimensioning the fluid dispensed from the nozzle opening forms a closed application surface, but that nevertheless on the side adjacent to the distribution channel the interval between the channel inputs is great enough to have a sealing surface of sufficient size to be able to seal off the output channels by the piston reliably. Furthermore, the piston does not have to be positioned so precisely to prevent an output channel from being closed only partially by the piston. 
         [0013]    The invention is further distinguished by the fact that the output channels have an essentially rectangular cross section. This is more favorable than round cross sections for production reasons, since rectangular cross sections can be milled more simply into the corresponding surface of the sub-block of the nozzle arrangement. 
         [0014]    According to an alternative exemplary embodiment of the invention, the distance between the output channels is chosen so that the fluid dispensed from the nozzle opening forms a closed application surface, which is desired in some applications. This achieves an especially uniform coating thickness when applying adhesive, in particular hot-melt glue. The uniformity of this coating thickness has a particular effect on the quality of the adhesive bond. In particular when gluing labels to transparent containers such as bottles, sections of surface with an increased or reduced application of adhesive give a negative impression. The delivery of the adhesive proposed here, through the output channels whose spacing is chosen so that a closed application surface results, fulfills the demand for a uniform thickness of the coating on the application surface, which is desired for example when gluing labels to transparent containers such as bottles. 
         [0015]    An alternative exemplary embodiment proposes that the distance between the output channels be chosen so that the fluid dispensed from the nozzle opening forms an application surface which is made up of a number of strips spaced at a distance from each other. In some applications it is not necessary to provide the entire contact surface with adhesive. It is sufficient here to apply the adhesive to the contact surface in several strips, spaced at a distance from each other. In this way it is possible to achieve a saving of adhesive without having to accept a significant reduction of the quality of the adhesive bond. 
         [0016]    The invention is further refined by having a rotatably supported screw spindle mesh with a threaded body that is rigidly connected to the piston. This arrangement makes it possible to adjust the position of the piston in the distribution channel precisely without tilting the piston, which could cause its sealing effect to be lost. In addition to the possibility of adjusting the piston position, the screw spindle also produces the effect that the position setting of the piston is preserved even under the pressure that builds up due to the fluid stream in the distribution channel. Alternatively, the linear displacement of the position of the piston can also be realized by a chain drive, which significantly reduces the required construction space. A design of this sort is described in detail in EP 1 501 640. 
         [0017]    A refinement of the invention consists in the screw spindle being coupled through a worm gear to a rotary knob for manually adjusting the position of the piston in the distribution channel. The use of a rotary knob to operate the screw spindle makes manual adjustment of the position of the piston simpler and more convenient. Depending on the installation situation, it can be beneficial to change the layout of the axis of rotation, for example when the apparatus is poorly accessible from one side. Such a change in the layout of the axis of rotation can be achieved by means of an appropriately designed worm gear. Furthermore, by using gearing, it is possible optionally to realize a transmission ratio, whereby it is both possible to adjust the position of the piston even more exactly, and the exertion of force which this requires can be reduced significantly. 
         [0018]    A preferred embodiment of the invention is distinguished by the fact that a latching element is situated between the screw spindle and the gear set and works together with the rotary knob, the gear set and the screw spindle in such a way that the piston is movable discontinuously by the distance between two output channels. The latching element consists of a spring-loaded ball, which snaps into a recess perceptibly after a rotation of 360°. A rotation of the latching element by 360° causes the piston to be shifted by exactly the distance between two output channels. Such a discontinuous movability of the piston by the distance between two output channels is helpful in order to ensure that an output channel has fluid flowing through it either completely or not at all. The screw spindle, the latching element and the piston are matched to each other so that the end of the piston which is in contact with the fluid is always positioned directly at the upper boundary surface of the last output channel with fluid flowing through it—viewed in the direction of flow of the fluid. Alternatively, the rotary knob and the worm gear can also be omitted, and the screw spindle can be rotated directly by actuating the latching element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention will now be described on the basis of an exemplary embodiment of the apparatus according to the invention for applying fluids such as adhesive, in particular hot-melt glue, onto a substrate that is movable relative to the apparatus, with reference to the accompanying drawings. The figures show the following: 
           [0020]      FIG. 1  is a perspective view of an apparatus according to the invention for applying fluids to a substrate that is movable relative to the apparatus. 
           [0021]      FIG. 2  is a front view of the apparatus from  FIG. 1 . 
           [0022]      FIG. 3  is a lower section according to  FIG. 2  in a partial section representation. 
           [0023]      FIG. 4  is an enlarged partial section representation according to the detail of the upper part of the nozzle arrangement identified in  FIG. 2 . 
           [0024]      FIG. 5  is a side view of the apparatus from  FIG. 1  for applying fluids to a substrate that is movable relative to the apparatus. 
           [0025]      FIG. 6  is a top view of the apparatus from  FIG. 1  for applying fluids to a substrate that is movable relative to the apparatus. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The apparatus  10  depicted in  FIG. 1  is used to apply fluids such as adhesive, in particular hot-melt glue, to a substrate that is movable relative to the apparatus  10  in the direction of arrow  72 . The apparatus includes an electropneumatically operable applicator valve  22 , which is connectable to a basic body  12 . On one side of basic body  12  a nozzle arrangement  70  is removably attached by means of threaded connections  44  and centered with pins  48  ( FIG. 2 ). The nozzle arrangement includes two partial blocks  50  and  52 . Apparatus  10  can be connected by a hose  20  to a fluid source (not shown). Apparatus  10  is supplied with electrical energy through connecting element  36 . Apparatus  10  can be fixed in its position with the help of fastening elements  38 . 
         [0027]    Electrically operable applicator valve  22  has an electrical connection  82  and a pressurized air connection  80 , by means of which a pressurized air source (not shown) can be connected. In this way the possibility is created of selectively interrupting or releasing the flow of fluid through basic body  12  and carrying out an intermittent application of adhesive. 
         [0028]    It can be seen from  FIG. 2  that nozzle arrangement  70  has an essentially slit-shaped nozzle opening  54  through which the fluid is dispensed and applied to the substrate. The nozzle arrangement includes a cylindrically shaped distribution channel  14  (see  FIG. 3  and  FIG. 4 ), in which a piston  16  is movably situated. Piston  16  is movable in distribution channel  14  by means of adjusting apparatus  58 . 
         [0029]    Adjusting apparatus  58  includes a holding apparatus  42 , which is removably attached to a surface  56  of basic body  12 . Also connected to holding apparatus  42  is a bearing plate  68 . A screw spindle  32  is rotatably supported in bearing plate  68  and in the surface  56  of basic body  12  by means of journal bearings. Screw spindle  32  can be turned by means of a rotary knob  24 . In the depicted exemplary embodiment, rotary knob  24  is connected to screw spindle  32  through a worm gear  26 , so that the axis of the rotary motion can be changed. This arrangement opens up the possibility of orienting the rotary knob  24  so that it is more accessible. This is particularly advantageous when there is not much construction space available for the apparatus  10 . Furthermore, holding apparatus  42  is equipped with a scale by means of which the exact position of piston  16  in distribution channel  14  can be ascertained. 
         [0030]      FIG. 3  depicts the flow of fluid from the fluid source (not shown) into distribution channel  14 . The fluid is transported by a means of conveyance (not shown), for example a pump, through hose  20 , which is connected to a hose connection  74 , in which a filter is situated, into a hole  64  located in basic body  12 . Hole  64  leads into a hole section  62  which is sealed above and below the mouth of hole  64  in a manner not depicted, with O-rings which are integrated into a cylindrical hollow body of applicator valve  22 . The fluid enters into a channel (not shown) in the hollow body of applicator valve  22 , oriented as an extension of hole  65 , in which valve needle  84  runs. Farther downstream the channel expands. In this expansion valve needle  84  also expands and forms a valve body, which is dimensioned so that the flow of fluid is interrupted by contacts of the valve body against complementary surfaces of the enlargement of the channel. Since the flow of fluid is interrupted by a shift of the valve body in the upstream direction, the after-dripping described earlier can be reduced. A detailed description of how such an applicator valve works can be found in EP 0 850 697. 
         [0031]    After the fluid has passed the valve seat, it flows on through hole  65 , which communicates with hole  66 , which is located in sub-block  50 . Hole  66  issues into distribution channel  14 , which is bounded and sealed laterally by sub-blocks  50  and  52  and on its first end face by sealing plate  46  and a sealing element  76  optionally screwed into it, and on its second end face by piston  16 . 
         [0032]      FIG. 4  shows additional details of a section of distribution channel  14  according to  FIG. 2 . Piston  16  has an end  34  which is in contact with the fluid, which forms a narrow annular gap between its outer circumferential surface and the inner surface of distribution channel  14 , so that the section of distribution channel  14  occupied by piston  16  is sealed off and no fluid can penetrate into this section. Furthermore, sub-block  50  has output channels  18 , which communicate with the section of distribution channel  14  filled with fluid and with nozzle opening  54 . The fluid conveyed into distribution channel  14  flows on through the opened output channels  18   a  and  18   b  to nozzle opening  54 , through which the fluid is dispensed and applied to the substrate. The output channels designated in  FIG. 4  as  18   c  are closed by the piston and have no fluid flowing through them. The position of the piston can be used to choose the ratio of output channels with fluid flowing through them and closed output channels, and to vary the width of the resulting application surface. It is beneficial to the technology of flow for the output channels to be either completely open or completely closed. A partially opened output channel would cause irregularities in the fluid supply, so that uniform application would not be achieved. Piston  16  is positioned so that a largely offset-free and edge-free transition results in distribution channel  14  between the piston end  34  and the last output channel  18   b  through which fluid flows. This is achieved, as shown in  FIG. 4 , when piston end  34  is positioned flush with an upper boundary surface  78  of the current last output channel  18   b  through which fluid is flowing. The corresponding positioning of piston  16  is achieved by providing a latching element  28  between worm bear  26  and screw spindle  32  ( FIG. 2 ), which causes piston  16  to be moved discontinuously by the distance between two adjacent output channels  18 . 
         [0033]      FIG. 5  shows a side partial section view of the apparatus  10 . It can be seen how piston  16  works together with distribution channel  14 , sealing plate  46  and an optional sealing element  76 , and output channels  18 . It can also be seen from the figure that the rotation of rotary knob  24  is transferred through worm gear  26  to screw spindle  32 , and how the rotary motion is converted to a linear motion by means of threaded body  30  and transferred to piston  16 , which is rigidly connected to threaded body  30 . It is also evident where the fastening elements  38  are attached to basic body  12 . In the background the side parts of applicator valve  22  can be recognized, in particular the side connection  82  for the pressurized air supply. 
         [0034]    In  FIG. 6  the apparatus  10  is shown in a top view. Here the two sub-blocks  50  and  52 , which attach to basic body  12  and form nozzle opening  54 , become visible. In addition, the position of screw spindle  32  and of piston  16  in relation to each other and the position of rotary knob  24  are readily visible. Furthermore, the figures show the fastening element  38 , the two connections  80  and  82  for the supply of pressurized air to applicator valve  22  and the cable connection  36  for supplying the apparatus with electrical energy.