Abstract:
An applicator for applying liquid media to a material strip that can be moved relative to the applicator includes a housing having a drum chamber, a drum gate supported within the drum chamber and adapted to rotate therein, and a nozzle block spring-mounted to the housing. The nozzle block includes an inner surface communicating with the drum gate and a linear nozzle adapted to apply the liquid media to the material strip.

Description:
[0001]     This application claims the priority of German Application Serial No. DE 102004034422.1 filed on Jul. 15, 2004.  
       TECHNICAL FIELD  
       [0002]     The invention pertains generally to an applicator for applying liquid media, for example, liquefied thermoplastic polymers or molten hot melt adhesives to a material strip that can be moved relative to the applicator.  
       BACKGROUND  
       [0003]     An applicator for applying liquid is shown in DE 102 16 356 C1 (the DE &#39;356 application). The DE &#39;356 application discloses axially parallel surface grooves arranged on a drum gate. More specifically, the applicator respectively comprises first grooves that apply the liquid medium on the material strip in the form of a line that extends perpendicularly to the direction that the material strip moves, as well as second surface grooves for accommodating sealing lips that adjoin the surface of the drum chamber under prestress. One respective second surface groove is assigned to each first surface groove such that it trails the first surface groove during the rotation of the drum gate. This is intended to prevent liquid medium from continuing to flow into the supply lines leading to the linear nozzle from the gap between the drum gate and the drum chamber, the thickness of which lies on the order of 0.02 mm, after the first surface groove moves past said supply lines. This particular concept with second surface grooves for accommodating sealing lips cannot be used in connection with surface grooves that have a more complicated progression on the cylinder surface, e.g., in the form of a closed, continuous line.  
       SUMMARY OF THE INVENTION  
       [0004]     Based on these circumstances, the invention aims to make available an applicator of the above-described type that ensures a highly selective application of liquid media on material strips. This objective is achieved in that the linear nozzle is positioned in a nozzle block that is spring-mounted to the housing and adjoins the drum gate under prestress. This ensures a gap-free contact in the region in which the liquid medium flows from the surface groove of the drum gate into the supply lines leading to the linear nozzle regardless of the aforementioned gap in the form of a cylinder jacket that is formed between the drum gate and the drum chamber, which must be provided in any case in order to compensate for different thermal expansions. Thus, a so-called reapplication is prevented after the surface groove moves past the linear nozzle, i.e., the medium is applied to the material strip in highly selective fashion with the shape and width of the surface groove in the drum gate. Clean boundaries of the applied liquid medium are also advantageous with respect to the additional processing of the material strip.  
         [0005]     According to one advantageous embodiment, the inner cylindrical contact surface of the nozzle block on the drum gate is adapted to, or shaped to cooperate with, the cylindrical surface of the drum gate.  
         [0006]     According to another advantageous embodiment, the drum gate comprises 
        an inner cavity that can be a supplied with liquid medium,     at least one surface channel that can be supplied with liquid medium from the inner cavity and is able to communicate with the linear nozzle as a function of the rotational position, and     radial outlet bores that lead from the inner cavity into the at least one surface channel.        
 
         [0010]     An applicator according to the invention provides the advantage that the nozzle block controls the medium with clean contours at the inlet openings to the supply lines leading to the linear nozzle such that the precision of metering the liquid medium is not disadvantageously influenced by the viscosity of the medium or the elasticity of the medium. Flawless application results can be obtained over the entire length of the applicator due to the defined supply of the liquid medium from the inner cavity of the drum gate to the linear nozzle.  
         [0011]     According to a first embodiment, a transverse bore is provided in the housing on at least one end thereof, and an annular channel is arranged between the drum gate and the drum chamber and connected to the transverse bore in the housing. In addition, radial supply bores are arranged in the drum gate in the plane of the annular channel, wherein said supply bores are connected to the inner cavity and serve for supplying the respective medium. At least one annular channel or groove may also be provided in the drum surface and/or the periphery of the drum chamber.  
         [0012]     According to an alternative embodiment, the drum gate is provided with at least one pin that axially protrudes from the housing and contains an axial bore that is connected to the inner cavity and serves for supplying the medium to the inner cavity. Although this results in a particularly simple design of the housing, it is necessary to provide a rotary seal in the region in which the pressurized medium is supplied to the pin.  
         [0013]     In both above-described embodiments, it is necessary to provide a reliable seal between the housing and the surroundings as well as a peripheral seal between the nozzle block and the housing.  
         [0014]     One preferred embodiment is illustrated in the figures and described below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1A  is a side view of an applicator according to the invention in its entirety;  
         [0016]      FIG. 1B  is a top view of an applicator according to the invention in its entirety;  
         [0017]      FIG. 1C  is an orthogonal longitudinal cross section of an applicator according to the invention in its entirety;  
         [0018]      FIG. 2  is a cross sectional view of the applicator according to  FIG. 1  taken along line  2 - 2  in  FIG. 1C ;  
         [0019]      FIG. 3  is a cross sectional view of the applicator according to  FIG. 1  taken along line  3 - 3  in  FIG. 1C ;  
         [0020]      FIG. 3A  is an enlarged detail of encircled area  3 A shown in  FIG. 3 ;  
         [0021]      FIG. 4  is a perspective view of the drum gate;  
         [0022]      FIG. 4C  is a perspective view of an applicator treated material strip;  
         [0023]      FIG. 5A  is a perspective view of the drum gate with channel progressions shown with hidden lines;  
         [0024]      FIG. 5B  is a perspective view of entire applicator; and  
         [0025]      FIG. 5C  is a perspective view of an applicator treated material strip. 
     
    
     DETAILED DESCRIPTION  
       [0026]      FIGS. 1A, 1B ,  1 C shows an applicator  11  of oblong cubical shape. The following description applies to all illustrations in this figure. The multipart housing  12  of the applicator contains a drum gate  13  that can be rotatively driven via a pin  15  that protrudes from the housing. A nozzle block  17  is situated on the underside of the housing, wherein a portion of said nozzle block is inserted into the housing  12  in a fitted and sealed manner and in direct contact with the drum gate  13 . A linear nozzle  18  consisting of a row of bores or dispensing outlets is arranged in the nozzle block  17 . The drum gate  13  is supported in the housing by a first pin  14  and the aforementioned protruding pin  15 . The pins  14 ,  15  respectively rotate in bearing sleeves  19 ,  20 . Transverse bores  21 ,  22  situated in the housing serve for supplying the liquid medium to a cylindrical drum chamber  23 , in which the drum gate is seated in an essentially gap-free fashion. The drum gate contains respective intersecting, radial supply bores  24 ,  25  in the planes of the transverse bores  21 ,  22 , one of which is illustrated in the form of a section along  2 - 2 . The outer ends of these intersecting bores are respectively connected to one another by peripheral grooves or annular channels  26 ,  27 . The intersecting bores extend through a central inner cavity  28  in the drum gate  13 . Liquid medium is continuously supplied to the central inner cavity  28  in the drum gate  13  via the peripheral grooves  26 ,  27  that constantly communicate with the transverse bores  21 ,  22  and via the intersecting bores  24 ,  25 . The liquid medium is then delivered from the central inner cavity  28  to a surface channel  32  in the drum gate via a plurality of radial outlet bores in the drum gate, three ( 29 ,  30 ,  31 ) of which are indicated in the form of examples. This surface channel in the drum gate forms a closed curve and is described in greater detail further below. Defined regions of the linear nozzle  18 , i.e., certain individual bores, are supplied with liquid medium via the surface channel  32  within such defined time intervals that the liquid medium can emerge from the linear nozzle within defined time intervals.  
         [0027]     Section  2 - 2  according to  FIG. 2  shows the housing  12  in the form of a block, the drum gate  13 , and the nozzle block  17 . This figure also shows the transverse bore  22  in the housing  12  that extends as far as the drum chamber  23  and is widened on the outside such that it forms a coupling sleeve. The intersecting bore  25 , the peripheral groove  27  and the central inner cavity  28  are individually illustrated in the drum gate  13 .  
         [0028]     The section  3 - 3  according to  FIG. 3  shows the housing block  12  and the drum gate  13  with the central inner cavity  28  and one of the radial outlet bores  30  originating at this cavity. The radial bore  30  communicates with one of the individual bores of the linear nozzle  18 . In the position shown, the liquid medium can be conveyed from the central inner cavity  28  to a certain section of the linear nozzle  18 . The nozzle block  17  is fitted into an opening of the housing  12  where it is sealed several times. The nozzle block directly adjoins a portion of the drum gate  13  under prestress with a hollow cylindrical surface  33 . In order to generate this prestress, the nozzle block  17  is held by screws  34 ,  35  and elastically supported relative to the housing  12  on the heads of these screws by means of disk springs  36 ,  37 . This is illustrated particularly well in  FIG. 3A .  
         [0029]     The following description applies to  FIGS. 4A through 5C . These figures show a detail of the drum gate  13  with its pins  14 ,  15  and the peripheral grooves  26 ,  27  in the region of the intersecting bores  24 ,  25 . These figures also show the surface channel  32  that extends over the cylindrical surface of the drum gate  13  and forms a closed curve. When liquid medium is supplied via the transverse bores  21 ,  22 , a rotation of the drum gate by 360° causes the medium to be applied to a material strip  41  transported perpendicularly to the drum gate in the form of a curve  42  that corresponds to a developed view of the peripheral groove  32 . In this respect, the circumferential speed on the surface of the drum gate  13 , ideally, is approximately equal to the transport speed of the material strip. The perspective view with hidden lines according to  FIG. 5A  also shows the intersecting bores  24 ,  25 , the central channel  28 , some of the radial bores  29 ,  30 ,  31  and the surface channel  32  that is supplied by all transverse bores.