Abstract:
The invention relates to an application head for dispensing a free-flowing medium. The application head comprises an injection chamber inside the application head and an injection needle movably mounted inside the injection chamber. An opening movement of the injection needle opens an outlet. A supply channel and a supply line are also provided in order to introduce the free-flowing medium into the injection chamber. A drive generates the opening movement of the injection needle. The application head also comprises a lever arm, the first end of said arm being movably fixed to a rear end of the injection needle and the second end thereof being connected to the drive. A membrane suspension comprising a membrane is provided, and the lever arm extends through the membrane of the membrane suspension. The membrane suspension is used to movably connect the lever arm to the application head, and as a seal to prevent the free-flowing medium from leaking out.

Description:
DESCRIPTION 
       [0001]    The invention relates to an application head for dispensing a free-flowing medium and application device having at least one such application head. In particular, it relates to dispensing adhesives and the use of hot glue. The invention can also be used for the controlled dispensing of cold glue or glue which comprises aggressive (e.g., corrosive) components. 
         [0002]    The priority of application EP 10 151 806.6, which was filed on 27 Jan. 2010 with the European Patent Office, is claimed. 
       BACKGROUND OF THE INVENTION, PRIOR ART 
       [0003]    In numerous industrial manufacturing processes, adhesives, sealants, and similar free-flowing media are used, which are applied or sprayed in liquid form onto a workpiece or substrate. 
         [0004]    The corresponding application heads must be robust and allow precise, high-precision dispensing of the medium. The application heads are simultaneously to be rapidly switchable, in order to be able to portion out adhesive quantities or apply them precisely in points or strips. In addition, the application heads are not to be excessively large, since frequently only limited space is available in the corresponding application devices. 
         [0005]    Further problems arise if hot glue is to be processed. Thus, for example, the great heat in the interior of an application head can damage the drive unit. There are also types of glue which contain additives, which can be aggressive. The pH value of a glue can thus be in the acid range, for example. Glue can also contain corrosively or abrasively acting components. In order to protect an application head therefrom, suitable measures must be taken. 
         [0006]    The problem presents itself of providing a precisely operating and reliable application head which avoids or entirely remedies a part of the disadvantages of previously known solutions. 
         [0007]    The problem is solved by an application head according to Claim  1  and by an application device having corresponding control module according to Claim  6 . 
         [0008]    A first application head according to the invention is especially designed for dispensing a free-flowing medium. It comprises a (nozzle) chamber in the interior of the application head and a nozzle needle, a needle valve, or a slide (designated here in summary as a “movable element”), which is mounted so it is movable in the interior of the nozzle chamber. The movable element executes a movement and releases an outlet opening for a short time in each case. The application head can also act in reverse, in that the movable element closes an outlet opening for a short time in each case. A supply channel is provided, which is connected to the (nozzle) chamber and is connectable with respect to flow to a supply line. The free-flowing medium can be introduced into the (nozzle) chamber through the supply line and the supply channel. A drive generates the opening movement or closing movement of the movable element. A lever arm is provided, whose first extremal end is fastened so it is movable on a rear end of the movable element and whose second extremal end is connected/coupled to the drive. Furthermore, the application head comprises a membrane suspension having a membrane. The lever arm extends essentially perpendicularly through a surface spanned by the membrane of the membrane suspension. The membrane is used for the purpose of connecting the lever arm to the application head so it is movable. Furthermore, the membrane suspension is used as a seal to prevent an escape of the free-flowing medium from the (nozzle) chamber. In addition, the membrane is preferably implemented so that it is resistant in relation to the free-flowing medium. In all embodiments, the membrane is preferably temperature-resistant and/or corrosion-resistant and/or abrasion-resistant and/or resistant in relation to chemical additives in the medium. 
         [0009]    Depending on the embodiment, the membrane can comprise at least one sealing ring, which is used as a seal and for elastically clamping the membrane in the application head. This embodiment can be used in all embodiments of the invention and offers an improved seal in relation to escaping adhesive, for example. 
         [0010]    An embodiment is particularly preferred in which there is a metallic membrane, which can execute back and forth movements particularly rapidly and therefore allows rapid opening or closing of the outlet opening. Such a metallic membrane is particularly suitable for alternating load at high frequency, i.e., for embodiments in which very rapid opening or closing is required. A metallic membrane is particularly advantageous and can be used in all embodiments of the invention. 
         [0011]    The invention is very particularly suitable for thermoplastic (hot melt) adhesives. However, it is also suitable for aggressive types of glue and, e.g., for cold glue. 
         [0012]    Further advantageous embodiments of the invention are set forth in the dependent claims. 
     
    
     
       FIGURES 
         [0013]    Further details and advantages of the invention are described in greater detail hereafter on the basis of exemplary embodiments and partially with reference to the drawings. All figures are schematic and are not to scale and corresponding structural elements are provided with identical reference numerals in the various figures, even if they are differently formed in detail. It shows: 
           [0014]      FIG. 1  a schematic perspective view of a first embodiment of the invention; 
           [0015]      FIG. 2  a schematic sectional view of a further embodiment of the invention; 
           [0016]      FIG. 3A  a top view of a membrane of a further embodiment of the invention; 
           [0017]      FIG. 3B  a perspective sectional view of a membrane suspension of a further embodiment of the invention; 
           [0018]      FIG. 4  an enlarged schematic sectional view of a further embodiment of the invention; 
           [0019]      FIG. 5  a schematic side view of a further embodiment of the invention; 
           [0020]      FIG. 6A  a sectional illustration of a further embodiment of the invention in which a preferred thermally-decoupled connection between a drive and an application head can be recognized; 
           [0021]      FIG. 6B  an enlarged sectional illustration of  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
       [0022]    The principle of the invention will be described hereafter on the basis of a first embodiment.  FIG. 1  shows an application device  100  having multiple application heads  15  arranged in a row, nozzle outlet openings  12 , and having individually switchable adhesive supply lines  16 . Instead of the nozzle outlet openings  12  shown, other outlet openings  12  can also be used. The shape, arrangement, and design of the outlet openings  12  can be dependent on whether a nozzle needle, a needle valve, or a slide is used as the movable element  11  in the interior of the application head  15 . 
         [0023]    Each of the outlet openings  12  is implemented on or in a respective application head  15 . Each application head  15  is especially designed for dispensing a free-flowing medium M, preferably adhesive, and comprises a (nozzle) chamber  10  in the interior of the application head  15 . In the example shown, a nozzle needle  11  is mounted so it is movable up and down in the interior of the (nozzle) chamber  10 , the nozzle needle releasing the outlet opening  12  through an opening movement P of the nozzle needle  11 . An arrow P is shown in  FIG. 2 , which is directed upward. An opening movement in arrow direction P raises the nozzle needle  11  and the needle releases the outlet opening  12 , so that the medium M can escape from the nozzle chamber  10  through the outlet opening  12 . In  FIG. 1 , four application heads  15  simultaneously permanently dispense a medium M in strip-shaped webs (beads). The strip shape arises because of the passing movement of a paper web K or a workpiece or a substrate. The corresponding movement direction is identified by V. 
         [0024]    In the interior, a supply channel  13  is provided, which is connected to the (nozzle) chamber  10 . The supply channel  13  is connectable with respect to flow to a supply line  16 , in order to be able to introduce the free-flowing medium M into the (nozzle) chamber  10 . Four separate supply lines  16  are indicated in  FIG. 1 . However, a common supply line  16  can also be used for multiple application heads  15 . 
         [0025]    Furthermore, a drive  20  is provided for generating the opening movement P of the nozzle needle  11 . In  FIG. 1 , the drive  20  is attached or flanged on the application heads  15 . The drive  20  preferably comprises a separate drive  20  per application head  15 , so that each outlet opening  12  can be opened and closed individually (i.e., independently of the others). 
         [0026]    Embodiments in which the drive  20  is arranged spaced apart from the application head  15 , as can be seen in  FIG. 2 , for example, are particularly preferred. However, it is important in the arrangement of the drive  20  in relation to the application head  15  (this statement applies for arrangements according to  FIG. 1  and  FIG. 2 ), that the mutual spacing is precisely defined and stable. This aspect is important, since any spacing change can have an influence on the function or mode of operation of the lever arm  30 . Details on the lever arm  30  are described hereafter. 
         [0027]    Further details will be explained on the basis of another embodiment, which is shown in a section in  FIG. 2 .  FIG. 2  shows a section through an individual application head  15 , in which the drive  20  is arranged spaced apart (i.e., spatially separated). According to the invention, the application head  15  comprises one lever arm  30  per drive  20 , whose first extremal end  31  is fastened so it is movable on a rear end  14  of the nozzle needle  11  or another movable element and whose second extremal end  32  is connected to the drive  20 . A membrane suspension  33  having a membrane  34  is used, the lever arm  30  extending through the membrane  34  of the membrane suspension  33 . The membrane suspension  33  is used for the purpose of connecting the lever arm  30  to the application head  15  so it is movable. In addition, the membrane suspension  33  is used as a seal to prevent the free-flowing medium M from escaping from the (nozzle) chamber  10 . I.e., the membrane  34  or the membrane suspension  33 , respectively, has a double function. In addition, depending on the design of the membrane  34 , it has a protective function in relation to temperature, corrosion, abrasion, and chemical additives of the medium M. 
         [0028]    The following further details distinguish this embodiment. The (nozzle) chamber  10  is implemented so that in its lower region, close to the outlet opening  12 , a stop point  17  or a stop surface (also referred to as a needle seat), respectively, is provided for the tip  18  of the nozzle needle  11 . In  FIG. 2 , the nozzle needle  11  is shown in the closure position, i.e., the tip  18  of the nozzle needle  11  is seated sealed on the stop point  17  and no medium M can escape through the outlet opening  12 . As soon as the nozzle needle  11  is raised by the opening movement P, the outlet opening  12  is released and medium M can escape. 
         [0029]    The nozzle needle  11  is connected so it is movable (like a toggle joint) to the lever arm  30  in the region of the rear end  14 . The nozzle needle  11  more or less “dangles” in the nozzle chamber  10 . Because the nozzle chamber  10  and the nozzle needle  11  are implemented as conically rotationally-symmetric in the lower area (close to the stop point  17 ), the nozzle needle  11  is guided centered during a downward movement. In addition, the medium M, which flows from the supply channel  13  through the (nozzle) chamber  11  in the direction of outlet opening  12 , contributes to stabilization or self-centering, respectively, of the nozzle needle  11 . This type of “dangling” mount or suspension can be applied in all embodiments. 
         [0030]    The lever arm  30  is implemented here so that it comprises a flat, rectangular, or strip-shaped rod, which is optionally provided with holes  39  here. The holes  39  are used to make the rod lighter, to reduce the mass to be accelerated. In addition, the holes  39  allow a displacement of the attachment point A of the drive  20 . Therefore, if the effective lever arm is to be lengthened, the drive  20  (or the attachment point A, respectively) can be shifted further in the direction of the second extremal end  32  and vice versa. In the example shown, the drive  20  is seated almost on the extremal end  32 , i.e., the effective lever arm is relatively long. The closer the drive  20  (or the attachment point A, respectively) is displaced in the direction of the membrane suspension  33 , the shorter the effective lever arm. A step-down transmission occurs in the case of a long lever arm, i.e., a large movement P 1  causes a small movement P in the opposite direction. The step-down factor in  FIG. 2  is approximately 5:1 (i.e., the absolute value of the movement P 1  is approximately 5 times as large as the absolute value of the movement P). In the case of a small lever arm, a step-up transmission occurs, i.e., a small movement P 1  causes a large movement P in the opposite direction. 
         [0031]    However, the lever arm  30  can also have any other rod or lever shape. The lever arm  30  is preferably manufactured from torsion-resistant material. In addition, the lever arm  30  is to be as light as possible, in order to have a small moved or accelerated mass. The membrane  34  is used in all embodiments as a kinematic support, which carries/mounts a part of the mass of the lever arm  30 . In addition, the membrane  34  defines the precise pivot or tilting point (referred to as the virtual pivot axis) of the lever arm  30  in all embodiments. 
         [0032]    In order to be able to mount or hold the lever arm  30  in the membrane suspension  33 , a cylindrical rod  40  is provided on the lever arm  30  in the embodiment shown. This cylindrical rod  40  pinches or clamps the membrane  34  and therefore provides a suspension of the lever arm  30  on the membrane  34 . Details of an exemplary preferred arrangement can be inferred from  FIG. 4 . This type of the suspension can be applied in all embodiments. 
         [0033]    Furthermore,  FIGS. 2 and 4  show that the membrane  34  can comprise one or two sealing rings  35 , which allow the membrane  34  to be elastically clamped in the application head  15 . The sealing rings  35  are optional. For the purpose of clamping, the application head  15  can comprise a removable part or a lid (not shown in detail). If this part or this lid is removed, the membrane  34  including the optional sealing rings  35  can be inserted. The mentioned part or the lid is then fastened again and the membrane  34  is clamped. 
         [0034]      FIG. 4  shows that on the rear side of the membrane  34 , i.e., on the side which faces away from the (nozzle) chamber  10 , an optional pressure connecting part  38  is provided, which is used as a mechanical stop for the membrane  34 . Through this preferred embodiment, overstretching of the membrane  34  is prevented in the event of an overpressure in the nozzle chamber  10 . The membrane  34  is preferably designed and arranged in all embodiments so that it is only strained by bending, which lengthens the service life. 
         [0035]    A metallic membrane  34  is preferably used in the various embodiments, which is particularly suitable for alternating load at high frequencies. A membrane  34  in which either the entire membrane surface consists of metal, or in which a planar membrane substrate (e.g., made of plastic) is provided with a metal layer/metal vapor deposit, is designated as a metallic membrane  34 . 
         [0036]    Furthermore,  FIGS. 2 and 4  show that a counter movement P 1 , which is caused by the drive  20 , causes an opposing opening movement P of the nozzle needle  11 . The lever arm thus ensures a definition of the step-down or step-up transmission and a movement reversal. 
         [0037]      FIG. 3A  shows details of a preferred embodiment of the membrane  34 . The membrane  34  comprises slots  36  to increase the elasticity. In addition, a central opening  37  is provided, through which the lever arm  30  extends in the installed state. The location of the sealing ring or rings  35  is indicated in  FIG. 3A . This design of the membrane  34  is particularly suitable for metallic membranes  34 , in order to provide the metallic membrane  34  with the required elasticity. 
         [0038]    Through the special arrangement of the slots  36 , which nearly define a complete circle, two small webs  42  result at the positions three o&#39;clock and nine o&#39;clock. These two small webs  42  allow bending of the inner part  41  (i.e., the circular region  41  of the membrane  34  which is delimited on the outside in the radial direction by the slots  36 ) of the membrane  34 . The two small webs  42 , with the inner part  41  of the membrane  34 , quasi-define a virtual pivot axis VA. This virtual pivot axis VA is shown in  FIG. 3  by a dot-dash line. 
         [0039]      FIG. 3B  shows details of a preferred embodiment of a membrane suspension  33 . The fastening of the lever arm  30  on the membrane  34  can be seen here. This fastening is performed by the rod  40 , as described. In the embodiment shown, the rod  40  is internally hollow to reduce the weight. In order that no medium M can escape through the interior of the rod  40 , the rod  40  can be provided with caps  43  or sealing elements on both ends, for example. The location of the virtual pivot axis VA is also indicated in  FIG. 3B . The details shown in  FIG. 3B  may be applied to all embodiments. 
         [0040]      FIG. 5  shows details of a further embodiment of the invention. The arrangement of the elements is selected differently here, but the function is the same. A linear movement of the drive  20  is converted into an opening movement of the nozzle needle  11  in the interior of the application head  15 . The drive  20  is also implemented separately (i.e., spaced apart) from application head  15  here, as also in  FIG. 2 . 
         [0041]    In the various described embodiments, an
       electromagnetic or   pneumatic or   piezoelectric drive
 
is suitable as the drive  20 , which generates a corresponding linear movement P 1  (up and down movement) at the desired frequency, which is relayed by the effective active lever arm  30  through a step-down or step-up transmission to the nozzle needle  11  and induces the linear movement P therein. In the case of a piezoelectric drive  20 , however, one preferably operates with a step-up transmission, in order to convert the very small movements of the piezoelectric drive  20  into sufficiently large opening and closing movements P.
       
 
         [0045]    An electromagnetic drive  20  which is constructed according to the principle of a voice coil motor or a Lorentz coil has particularly proven itself. In this case, a 1:1 lever transmission ratio or a step-down transmission is particularly suitable in this case as the effective transmission ratio. A voice coil motor or a Lorentz coil can be used in all embodiments. 
         [0046]    The stroke in the region of the nozzle tip  18  or the outlet opening  12  is preferably between 0.1 mm and 1 mm. In the case of a 1:1 lever transmission ratio, the drive  20  must thus make a corresponding movement P 1  in the opposite direction having a stroke of 0.1 mm to 1 mm. 
         [0047]    With a suitable control of the drive  20 , e.g., via a driver module  21 , which can be arranged in the proximity of the drive  20 , as indicated as an example in  FIG. 5 , the movement behavior of the nozzle needle  11  or another movable element can be set or even regulated. If desired, a suitable movement profile can be stored, so that the nozzle needle  11  is decelerated shortly before it is incident on the stop point  17 . This measure lengthens the service life of the nozzle needle  11  and the application head  15 . A corresponding driver module  21  can be used in all embodiments. 
         [0048]    The greater the lever step-down transmission ratio is selected to be, the more precisely may the nozzle needle  11  be moved, because a large movement P 1  of the drive  20  is stepped down into a small movement P of the nozzle needle  11 . A disadvantage of such a large step-down transmission ratio, however, is the lengthened route which must be covered on the drive side. The achievable frequency or the maximum cycle, respectively, of the opening and closing movement of the nozzle needle  11  is thus possibly reduced. 
         [0049]    In a preferred embodiment, on the drive side, an intelligent controller (e.g., in the form of the driver module  21 ) of the drive  20  is designed so that the current which is fed into the drive  20  is observed. When the current increases, this is an indication that the nozzle needle  11  or the movable element is at the stop point  17 . Through an intelligent controller, a gradual adaptation of the movement profile stored in the driver module  21 , which can be defined in all embodiments by the cited parameterization, can be performed, which compensates for wear of the needle tip  18  in that the movement P 1  on the drive side is successively increased when the current signal indicates that the current increase only occurs later in relation to earlier. This is because the later occurrence of a current increase means that the needle tip  18  is at the stop point  17  later than heretofore. This is an indication of wear. The use of such an intelligent controller (e.g., in the form of the driver module  21 ) lengthens the service life of the application head  15 , since the nozzle needle  11  or the movable element must only be replaced later. 
         [0050]    In a preferred embodiment, on the drive side, an intelligent controller (e.g., in the form of the driver module  21 ) of the drive  20  is designed so that the movement of the nozzle needle  11  or the movable element is regulated according to a predefined movement profile. The switching times and the stroke of the nozzle needle  11  can be monitored and the application picture of the application head  15  can be automatically corrected by this controller. 
         [0051]    The driver module  21  is preferably located directly on each drive  20 , so that the drive  20  can be activated directly using a 24 VDC signal (also directly by a PLC) (PLC stands for programmable logic controller). This has the advantage that each application head  15  can be activated individually. A corresponding the driver module  21  can be used in all embodiments. 
         [0052]    In a preferred embodiment, on the drive side, an intelligent controller of the drive  20  is designed so that error, warning, service, or maintenance indicators are output. This approach can be used in all embodiments. 
         [0053]    It is an advantage of the invention that a spatial thermal separation (see, e.g.,  FIG. 5 ) is possible between drive  20  and the part of the application head  15  around which the medium M flows. Particularly in the case of warm or hot medium M, the problems are thus reduced which can otherwise be caused on the drive side due to the high temperature. 
         [0054]    The thermal separation between drive  20  and application head  15  is preferably achieved without a screw connection, as can be seen in  FIG. 6A  and the detail enlargement  6 B. An insulation plate  44  is laid on the application head  15 . The insulation plate  44  is implemented on the application head side having two positioning bolts  45  and on the drive side having four spacer/positioning bolts  46 . The fixation of application head  15  and drive  20  is performed via two cables  47  (preferably steel cables). A non-heat-conductive cable  47  is preferably used. The cables  47  are fixed on application head  15  at the point X 1  and are tensioned in the drive  20  by a tensioning device  48 . Through this arrangement, the application head  15  and the drive  20  are ideally fastened without a metallic connection (in the present arrangement solely by two thin cables  47 ). 
         [0055]    In all preferred embodiments, the lever arm  30  causes a reversal of the movement direction (P 1  points in the opposite direction as P; see  FIG. 2 ) and, depending on the setting of the lever arm lengths, a movement amplification (P&gt;P 1 ; referred to as step-up transmission) or a movement reduction (P 1 &gt;P; referred to as step-down transmission). In addition, the angled arrangement of the lever arm  30  in relation to the movable element  11  allows an arrangement of the membrane  34  in a region which is not directly subjected to the flowing medium M. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           10  (nozzle) chamber 
           11  movable element (e.g., nozzle needle) 
           12  outlet opening 
           13  supply channel 
           14  rear end of the nozzle needle  11   
           15  application head 
           16  supply line 
           17  stop point 
           18  tip 
           20  drive 
           21  driver module 
           30  lever arm 
           31  first extremal end 
           32  second extremal end 
           33  membrane suspension 
           34  membrane 
           35  sealing ring 
           37  slot 
           37  central opening 
           38  pressure connecting piece 
           39  holes 
           40  cylindrical rod 
           41  inner part of the membrane  34   
           42  webs 
           43  cap 
           44  insulation plate 
           45  positioning bolt 
           46  spacer/positioning bolt 
           47  cable 
           48  tensioning device 
           100  application device 
         A attachment point 
         K paper web 
         M free-flowing medium 
         V movement direction 
         VA virtual axis 
         P opening movement 
         P 1  counter movement 
         X 1  points