Abstract:
An apparatus for dispensing fluid includes a base member having a feed channel and a slot nozzle having first and second spaced apart members. A slot-shaped outlet channel is in fluid communication with the feed channel and is defined between the first and second spaced apart members. A slot-shaped outlet opening is in fluid communication with the slot-shaped outlet channel and has a width defined between the first and second spaced apart members. A valve is coupled with the base member and selectively interrupts and releases the flow of fluid through the slot-shaped outlet opening. An adjustment device infinitely adjusts the position of the first member relative to the position of the second member to change the width of the slot-shaped outlet opening. A method for dispensing fluid onto a substrate includes directing the fluid through the slot-shaped outlet channel while continuously increasing the pressure of the fluid.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a device and method for dispensing a fluid onto a substrate moving relative to the device, and more specifically to an intermittent dispensing device and method for dispensing films in a non-contacting manner.  
         BACKGROUND OF THE INVENTION  
         [0002]    Fluid dispensing devices, sometimes referred to as application heads, are used in various branches of industry to apply various fluid materials such as adhesives, paints or coating materials to sanitary articles, wood products, machine parts, vehicle body parts or the like, continuously or intermittently, in the form of a bead, as a line, as dots or over an area. The devices are connected to a source of fluid, for example, an adhesive reservoir, from which the fluid is directed through the feed channel to a nozzle, with the assistance of a pump if necessary. The fluid stream may be interrupted or released by a valve. When the valve is open the fluid flows through an outlet channel and emerges from an outlet opening of the nozzle under pressure and is then transferred to the substrate, which is moved relative to the outlet opening. In contact type devices the nozzle is in contact with the substrate while the fluid is being applied, while with non-contact devices a separation is maintained between the nozzle arrangement and the substrate.  
           [0003]    In industrial applications, various demands are made on the application pattern that develops on the substrate, that is, the three-dimensional or essentially two-dimensional extent of the applied fluid materials. With an essentially two-dimensional application, the nozzle is designed as a slot nozzle with an essentially slot-shaped outlet channel. This type of device produces sharply delimited lateral margins and maximally uniform, two-dimensional distribution of the fluid material with a surface that is as flat as possible. Frequently, it is also desirable or necessary to dispense relatively small quantities of fluid material per unit of area of the substrate surface.  
         SUMMARY OF THE INVENTION  
         [0004]    In one aspect of the invention, a fluid dispensing device is provided having an outlet channel with a steadily and evenly decreasing flow cross section or taper in the direction of flow of the fluid. A relatively high pressure builds up in the flowing fluid in the direction of flow. The fluid material then flows out of an outlet opening of the outlet channel at a relatively high speed and is then applied to the substrate. In particular, the fluid is to be applied by a method in which the substrate and the nozzle are not in contact with each other.  
           [0005]    Particularly when the nozzle is designed as a slot nozzle with an essentially slot-shaped outlet channel, and the flow cross section of the slot-shaped outlet channel according to the invention steadily decreases in the direction of flow of the fluid, i.e., in the direction toward the outlet opening, then according to the invention a sheet or film is dispensed at high speed from the slot-shaped outlet opening of the device and is applied or deposited uniformly on the substrate, which is moving relative to the device.  
           [0006]    Because of the tapering flow cross section of the slot-shaped outlet channel, a high pressure is produced in the fluid before the outlet opening, and a high speed is produced, and an extrusion-like production of film or sheet is achieved with uniform film or sheet thicknesses. Due to relatively small separations of about 2 to 10 mm between the outlet opening and the substrate surface, uniform application of a completely closed film is realized using the non-contact method.  
           [0007]    The invention provides for continuous variation of the flow cross section of the outlet channel of the nozzle. The flow conditions of the fluid, and in particular the pressure buildup, the flow rate and the width of the outlet opening may be easily varied and adapted to the particular case. For example, by reducing the flow cross section the pressure buildup may be increased and the flow rate increased. The width of the outlet opening may be varied to thereby vary the film thickness. For example, if a film having a small quantity of fluid per unit of area is to be dispensed onto the substrate, the width of the gap is reduced and the mass flow of the fluid is also reduced. According to the invention, specific fluid application quantities of two grams/m 2  to about 100 grams/m 2  can be produced on the substrate while realizing a closed film which may have a small film thickness, for example, of {fraction (1/10)} μm.  
           [0008]    In a preferred embodiment of the device according to the invention, the nozzle is designed as a slot nozzle with an essentially slot-shaped outlet channel which is bounded by two members spaced at a distance. An adjusting device is provided for continuous adjustment of one member relative to the other member so that the width of the essentially slot-shaped outlet channel is continuously variable. This embodiment is further refined by having at least part of one of the members bounding the slot-shaped outlet channel be elastically reshapable by the adjusting device in such a way that the width of the outlet channel is variable. A refinement of the adjusting device of simple design provides for the latter to have an adjusting bolt which acts on a projection of the elastically reshapable member. The elastic reshapability of the at least one member bounding the outlet channel may be simply realized by reducing or “thinning” the thickness of the material, for example, by reducing or tapering its cross section, so that when an adjusting force is applied with the adjusting device, an elastic reshaping of the body is produced in such a way that the outlet channel is enlarged or reduced. To produce thin sheets that are to be applied to substrates, the slot-shaped outlet channel is designed as a gap that tapers continuously out to the outlet opening. The width of the outlet opening, in the range between about 0.05 mm and 0.5 mm, is preferably adjustable.  
           [0009]    The fact that a pressurized air channel is contained inside the base body results in a compact design, without external hoses or tubes leading to the valve, and the entire construction volume is thereby reduced. The fact that the valve is located in a hole bored in the base body also produces a compact design, and the pressurized air can be fed through the pressurized air channel formed in the base body.  
           [0010]    Preferably, the flow cross section of the preferably slot-shaped outlet channel is reduced in such a way that the fluid is under a pressure of about 30 to 100 bar, preferably 40 to 70 bar, in the area of the outlet opening.  
           [0011]    According to another aspect of the invention, it is proposed that the fluid should flow through a gap that tapers continuously to a slot-shaped outlet opening and should emerge as a sheet from the slot-shaped outlet opening and then be deposited on the surface of the substrate without contact between the nozzle and the substrate.  
           [0012]    It is especially preferable for the fluid to be a constantly sticky hot melt pressure sensitive adhesive, and/or that the fluid be an acrylic-based or rubber-based adhesive or a UV-curing adhesive or some other thermoplastic material. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The invention is described below on the basis of an exemplary embodiment of a device and a method for dispensing and applying thermoplastic adhesives on a substrate, with reference to the attached drawings.  
         [0014]    [0014]FIG. 1 is a partially sectioned view of a device according to the invention for applying fluid.  
         [0015]    [0015]FIG. 2 is a side view of the device shown in FIG. 1.  
         [0016]    [0016]FIG. 3 is a sectional view of an upper part of a base body of the device shown in FIG. 1.  
         [0017]    [0017]FIG. 4 is a sectional view of a lower part of the base body of the device shown in FIG. 1.  
         [0018]    [0018]FIG. 5 is a top view of the lower part of the base body shown in FIG. 4.  
     
    
     DETAILED DESCRIPTION  
       [0019]    Application device  1  shown in the figures serves in general for applying fluid materials (fluids) onto substrates, and is adapted to the dispensing and application of fluid thermoplastic adhesives in the form of sheets on various substrates such as woven fabric, foil, paper or the like. Application device  1  includes essentially a two-part metal base body  2  that comprises an upper partial body  4  and a lower partial body  6 , a nozzle  8  designed as a wide-slot nozzle and as part of base body  2 , and a plurality of valves  10  (see also FIG. 2) for selectively interrupting or releasing the flow of the fluid. Valves  10  are pneumatically actuatable with pressurized air, and can frequently also be referred to as control units or control modules.  
         [0020]    A fluid feed channel  12  (FIG. 1) is formed in lower partial body  6  of base body  2 , and is coupled by a fluid fitting  14 , in a manner not shown, to a fluid source in the form of a reservoir containing adhesive. The exemplary embodiment is provided with two feed channels  12  (see FIG. 2), which are fed by gear pumps (not shown). Feed channel  12  has a plurality of sub-sections, specifically a first oblique bore  16 , a bore  18 , a channel  20  formed in body  4 , and in each instance an oblique bore  22  communicating with channel  20 . Oblique bore  22  issues into a bore  24  formed in partial body  4 , into which bore  24  a lower section of each valve arrangement  10  is inserted. Feed channel  12  has additional sections, specifically a bore  26  communicating with bore  24  (FIG. 1), a plurality of U-shaped channels  28  formed in the top of partial body  6  (see FIG. 5), and a distribution channel  30  of essentially semi-circular cross section communicating with the end sections of the sides of the U-shaped channels  28 .  
         [0021]    An outlet channel  32  of nozzle arrangement  8  is then connected to transverse distribution channel  30 . Outlet channel  32  is slot-shaped in the exemplary embodiment, and has an elongated outlet opening  34  (see FIGS. 1 and 2), through which the fluid is dispensed in the form of a sheet or a film and is then applied onto a substrate (not shown). The direction of relative motion between application device  1  and substrate is indicated by arrow  36 . Elongated slot-shaped outlet opening  34  extends perpendicular to the drawing plane in FIG. 1.  
         [0022]    As FIGS. 4 and 5 show, a total of four U-shaped channels  28  are formed on the top side of lower body  6  and lie essentially in a horizontal plane. Bores  26  communicate with the transverse sides  29  of channels  28 , so that fluid is distributed to the two further sides of channels  28  across the width of application device  1 . The fluid is then further distributed transversely in the transverse distribution channel  30 , which communicates with outlet channel  32  (FIG. 1).  
         [0023]    As FIG. 2 shows, transverse distribution channel  30  is laterally bounded and sealed by side hatches  38 , to which sealing elements of plastic, preferably PTFE (polytetrafluoroethylene) are affixed by means of screws  40 . Base body  2  is closed at the sides by opposing metal plates  42 , which are attached using screws  44 .  
         [0024]    Using a plurality of adjusting screws  46  (see FIG. 1), each assigned to a channel  28  (FIG. 5), which may be screwed into threaded holes  48  (see FIG. 3) formed in upper body  4 , it is possible to vary the free flow cross section in channels  28  by screwing the flat-ended screws  46  in to varying depths, so that the flow of fluid through channels  28  may be varied and finely adjusted due to differing flow resistances.  
         [0025]    The valve arrangement  10  connected into feed line  12 , which is designed in the manner of a control unit, has its lower section inserted into bore  24  of base body  2 , and only the upper section protrudes from base body  2 . Valve  10  has a valve body  52  that moves together with a valve needle or valve stem  50  and interacts with a valve seat  54  formed on the body  4  of base body  2  in such a way that the flow of fluid into feed channel  12  and thus through the entire application device  2  and in particular through outlet opening  34  may be selectively interrupted or released. To this end, valve body  52  is moved axially up or down together with valve stem  50  by means of a piston  56 , which passes through and is sealed in bore  24 . In a manner not shown in further detail, above piston  56  is a cylinder chamber constantly filled with pressurized air, which may be filled with pressured air by a pressurized air connection line  58  (FIG. 2) and channels formed in valve  10 , in order to press piston  56  and valve body  52  into the closed position.  
         [0026]    A pressurized air channel  58  formed in upper body  4  of base body  2  leads to a cylinder chamber  60  located below piston  56 , so that pressurized gas may be introduced into this chamber at a pressure such that piston  56  and valve body  52  are moved upward and into the open position, so that the flow of fluid is released. Pressurized air channel  58  is attachable to a source of pressurized gas by a connection  62 . An electrically controllable valve, not shown, introduces pressurized air selectively into pressurized air channel  58  to open valve  10 . When a large application width is to be achieved, a large number of application valves  10  may be connected in series, and correspondingly a large number of pressurized air channels  58  may be formed in base body  2 . Pressurized air is then introduced into the plurality of pressurized air channels  58  by a transverse distribution channel  64 . Line  58  is connected to a source of pressurized air by a connection  66  (FIG. 2). Inserting valves  10  into bore  24  and forming pressurized air channels  58  in base body  2  (of body  4 ) results in a compact design without troublesome external connecting lines.  
         [0027]    The geometry and the variability of the geometric conditions of outlet channel  32  of nozzle  8  are explained in greater detail below. In the exemplary embodiment, nozzle  8  is designed as a slot nozzle, and outlet channel  32  is slot-shaped and is designed as a gap that tapers down continuously to outlet opening  34 . The flow cross section of outlet channel  34  thus becomes smaller in the direction of flow of the fluid. In a manner not shown, alternatively and according to an alternative exemplary embodiment, outlet channel  32  could be design as a cylindrical, conically tapered bore whose flow cross section also becomes continuously smaller until outlet opening  34 . In the exemplary embodiment shown, outlet channel  32  is bounded (as FIG. 1 shows) by a section of upper body  4 —located to the right in FIG. 1—and an opposing section—to the right section in FIG. 1—of lower body  6  of base body  2 . The opposing surfaces  68 ,  70  (see FIGS. 3 and 4) of opposing bodies  4 ,  6  are ground and polished in the area of outlet channel  32 . Outlet channel  32  is designed as a continuously tapering gap.  
         [0028]    Application device  2  according to the invention includes an adjusting device  72  for continuously varying the flow cross section of outlet channel  32  of nozzle arrangement  8 . In the exemplary embodiment adjusting device  72  (FIG. 1) provides for infinitely variable adjustment of at least one section of body  4  relative to the opposing body  6  in the area of outlet channel  32 . Adjusting device  72  has an adjusting bolt  74  which has outside threading and has one end screwed into a threaded bore  76  of body  4 . Bolt  74 , which protrudes in front of body  4 , is inserted through a through bore  80  in a projection  78  of body  4 . A nut  82  secures bolt  74  axially relative to body  4 . With the help of two additional nuts  84 ,  86  which are screwed onto bolt  74 , it is possible to apply an adjusting force that acts essentially in the longitudinal direction of bolt  74  to projection  78  of body  4 , so that, as indicated by arrow  88  in FIG. 1, a torque is applied to projection  78  in such a way that by tightening nuts  84  or  86  either a certain spreading of section  90  of body  4  results and the width of the slit-formed outlet channel  32  increases and thus the flow cross section increases, and also the width—measured in the direction of the relative motion direction  36 —outlet opening  34  increases or decreases. This makes continuously variable adjustment or variation of the width and flow cross section of outlet channel  32  possible.  
         [0029]    This adjustment is made possible by an elastic ductility of body  4 , or more precisely, of section  90  of body  4  in the area of outlet channel  32  due to the application of force by means of adjusting device  72 . Due to a recess  34 , essentially U-shaped in cross section, section  90  has a section  96  of relatively small thickness, in which especially great elastic deformability is possible.  
         [0030]    As FIG. 2 makes clear, in the illustrated exemplary embodiment a multiplicity of seven adjacent adjusting devices  72  are provided with seven bolts  74  which act on projection  78  of body  4 , and which make it possible to uniformly and continuously vary the geometry, in particular the width and the flow cross section of outlet channel  32  and of outlet opening  34  of nozzle  8  over the entire width of nozzle  8 , by appropriate adjustment of nuts  84 ,  86 . It is especially preferable to set a width of the outlet opening of outlet channel  32  between 0.05 mm and 0.5 mm by operating the adjusting device  72 . The width is measured between the apexes  69  and  71  of bodies  4  and  6  shown in FIG. 3.  
         [0031]    In operation liquid adhesive, for example, is directed into feed channel  12  by gear pumps. It is initially present under pressure at closed valve  10 . By introducing pressurized gas into pressurized air channel or channels  58 , valve  10  is brought to the open position and valve body  52  moves away from valve seat  54 , so that fluid flows through feed channel  12  and flows through outlet channel  32 , which has first been adjusted in the manner described above. The fluid emerges from outlet opening  34  in the form of a thin film or sheet. In the area of outlet channel  32 , fluid pressures in the range between 30 and 100 bar are produced. The fluid emerges at high speed from outlet opening  34  and is deposited on the surface of the substrate (not shown), which is moving relative to device  1  in the direction of arrow  36 . The substrate is positioned, for example, at a distance of 2 to 10 millimeters from outlet opening  34 . The relative speed and the mass flows of the fluid and the width adjustment of the flow cross section and the outlet opening  34  are matched to each other so that a uniform deposit of the generated sheet or film on the surface of the substrate is achieved. It is especially preferable for the fluid to be a constantly sticky hot melt pressure sensitive adhesive or an acrylic-based or rubber-based adhesive or a UV-curing adhesive.  
         [0032]    If valve  10  is brought to the closed position, the flow of fluid in feed channel  12  is interrupted, so that the flow of the fluid in outlet channel  32  and through outlet opening  34  is also interrupted. The width of outlet opening  34  may be varied by actuating device  72  as previously described.  
         [0033]    With the help of fasteners  98  it is possible to place device  1  in a stationary location in any desired orientation relative to the path of motion  36  of the substrate.