Abstract:
A system for dispensing liquid material with different configurations of air assisted fiberization or filament movement (e.g., meltblowing, controlled fiberization). In particular, front access for mounting a selected nozzle only requires adjustment of one lever and one fastener. Features of the lever and nozzle allow assisted ejection of the nozzle, even when the nozzle has become adhered to a die body through use. In addition, a nozzle mounting surface of the die body provides a universal interface to the various types of nozzles. An air cavity in the die body and air troughs in selected types of nozzles balance and adjust air flow.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is related to the following co-pending and commonly-owned applications which were filed on even date herewith, namely U.S. Ser. No. D______, entitled “Discharge Portion of a Liquid Filament Dispensing Valve” (Attorney Docket No. NOR-995 and Express Mail No. EL699929869US) and U.S. Ser. No. D______, entitled “Liquid Filament Dispensing Nozzle” (Attorney Docket No. NOR-996 and Express Mail No. EL699929872US), the disclosures of which is hereby incorporated by reference herein in their entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention generally relates to dispensing systems for applying a liquid material and, more particularly, for dispensing a filament or filaments of liquid, such as hot melt adhesive, on a substrate.  
         BACKGROUND OF THE INVENTION  
         [0003]    Various liquid dispensing systems use air assisted extrusion nozzles to apply viscous material, such as thermoplastic material, onto a moving substrate. Often times, these systems are used to form nonwoven products. For example, meltblowing systems may be used during the manufacture of products such as diapers, feminine hygiene products and the like. In general, meltblowing systems include a source of liquid thermoplastic material, a source of pressurized process air, and a manifold for distributing the liquid material and process air. A plurality of modules or dispensing valves may be mounted to the manifold for receiving the liquid and process air and dispensing an elongated filament of the liquid material which is attenuated and drawn down by the air before being randomly applied onto the substrate. In general, a meltblowing die tip or nozzle includes a plurality of liquid discharge orifices arranged in a row and a slot on each side of the row of liquid discharge orifices for dispensing the air. Instead of slots, it is also well known to use two rows of air discharge orifices parallel to the row of liquid discharge orifices.  
           [0004]    Controlled fiberization dispensing systems also use air assisted extrusion nozzles. However, the pressurized process air in these systems is used to swirl the extruded liquid filament. Conventional swirl nozzles or die tips typically have a central liquid discharge passage surrounded by a plurality of process air discharge passages. The liquid discharge passage is centrally located on a protrusion. A common configuration for the protrusion is conical or frustoconical with the liquid discharge passage opening at the apex. The process air discharge passages are typically disposed at the base of the protrusion. The process air discharge passages are usually arranged in a radially symmetric pattern about the central liquid discharge passage. The process air discharge passages are directed in a generally tangential manner relative to the liquid discharge orifice and are all angled in a clockwise or counterclockwise direction around the central liquid discharge passage.  
           [0005]    Another type of air assisted nozzle, referred to herein as a bi-radial nozzle, includes a wedge-shaped member having a pair of side surfaces converging to an apex. A liquid discharge passage extends along an axis through the wedge-shaped member and through the apex. The wedge-shaped member extends in a radially asymmetrical manner around the liquid discharge passage. Four process air discharge passages are positioned at the base of the wedge-shaped member. At least one process air discharge passage is positioned adjacent to each of the side surfaces and each of the process air discharge passages is angled in a compound manner generally toward the liquid discharge passage and offset from the axis of the liquid discharge passage.  
           [0006]    These and other types of air-assisted extrusion nozzles generally require periodic maintenance due to accumulation of dust, hardened liquid material, or other reasons. Each dispensing valve may have to be unbolted from the manifold by unscrewing at least two bolts. The nozzle is then removed from the dispensing valve and another nozzle is mounted onto the valve. If necessary, the valve is reattached to the manifold. Consequently, such repair can increase the required shut down time for removal and replacement of valves and nozzles. Removal of the entire dispensing valve with the attached nozzle is generally a requirement when changing between applications (e.g., meltblowing to controlled fiberization).  
           [0007]    For these reasons, it is desirable to provide apparatus and methods for quickly changing nozzles on a die assembly without encountering various problems of prior liquid dispensing systems. It is also desirable to provide for easier maintenance and replacement of air-assisted extrusion nozzles.  
         SUMMARY OF THE INVENTION  
         [0008]    Generally, the present invention provides an apparatus for dispensing a filament of liquid assisted by pressurized process air. The apparatus comprises a housing having a liquid supply passage, a process air supply passage, and a nozzle mounting surface which may be disposed within a recess of the housing. A nozzle includes an inlet side positioned adjacent the mounting surface and an outlet side having at least one liquid discharge orifice and a plurality of process air discharge passages adjacent the liquid discharge orifice. When properly mounted and aligned against the mounting surface, the liquid discharge orifice and the process air discharge air passages are respectively in fluid communication with the liquid supply passage and the process air supply passage of the housing. In one aspect of the invention, a nozzle ejecting lever is pivotally affixed to the housing and pivotally moves from a first position to a second position. In the first position, the nozzle may be mounted adjacent the mounting surface as described above and, as the ejecting lever is moved to the second position, the nozzle is pried away from the mounting surface. This assists in removing nozzles which may be otherwise adhered to the housing due to thermoplastic liquid or other reasons.  
           [0009]    In another aspect of the invention, a nozzle positioning lever is pivotally affixed to the housing to move between first and second positions. In the first position the positioning lever allows the nozzle to be mounted in a sealing manner within the housing recess and adjacent the mounting surface. In the second position the positioning lever holds the nozzle in the recess with the process air discharge passages in fluid communication with the process air supply passage and with the liquid discharge orifice in fluid communication with the liquid supply passage. In the preferred embodiment, the positioning lever and the ejecting lever may be one and the same with different portions of the lever performing the position and ejecting functions.  
           [0010]    In another aspect of the invention, a clamping lever is pivotally affixed to the housing and operates in conjunction with cam surfaces on the nozzle and the housing to clamp the nozzle within the housing recess. In the preferred embodiment, the positioning lever is used to first position the nozzle within the recess and temporarily hold the nozzle within the recess. The clamping lever is then used to fixedly secure the nozzle within the recess for the duration of the dispensing operation. For nozzle replacement, repair and other maintenance purposes, the clamping lever may be loosened and the positioning and ejecting lever may be used to pry the nozzle from the recess.  
           [0011]    A plurality of nozzles are provided in a liquid dispensing system in accordance with the invention, with each nozzle configured to discharge a different filament pattern. For example, a first nozzle may be configured to dispense meltblown filaments while a second nozzle may be configured to dispense a swirl filament pattern. Each of the nozzles is constructed to be received in the recess such that the liquid discharge orifice or orifices of the nozzle and the process air discharge passages are respectively in fluid communication with the liquid supply passage and process air supply passage of the housing. Each nozzle is symmetrically configured such that the nozzle may be rotated 180° and still be mountable within the housing recess. In this regard, the nozzle includes cam surfaces on opposite sidewall portions thereof which can each interchangeably engage the cam surface of the clamping lever or a cam surface formed on a wall of the recess.  
           [0012]    Various advantages, objectives, and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The accompanying drawings illustrate embodiments of the invention, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0014]    [0014]FIG. 1 is a cross-sectional view of a dispensing system configured to hold different types of air assisted extrusion nozzles in accordance with the principles of the present invention for dispensing liquid filaments;  
         [0015]    [0015]FIG. 1A is an enlarged cross-sectional view of a lower portion of the dispensing valve shown in FIG. 1, illustrating a nozzle assembly;  
         [0016]    [0016]FIG. 2 is a partially disassembled view of the dispensing valve including the nozzle shown in FIG. 1;  
         [0017]    [0017]FIG. 3 is perspective side view of the lower portion of the dispensing valve shown in FIG. 1;  
         [0018]    [0018]FIG. 4A is a cross-sectional view of the lower portion of the dispensing valve shown in FIG. 1, illustrating insertion of a nozzle, assisted by the positioning and ejecting lever;  
         [0019]    [0019]FIG. 4B is a cross-sectional view of the lower portion of the dispensing valve shown in FIG. 1, illustrating the nozzle being frictionally held by the positioning and ejecting lever;  
         [0020]    [0020]FIG. 4C is a cross-sectional view of the lower portion of the dispensing valve shown in FIG. 1, illustrating ejection of the nozzle, assisted by the positioning and ejecting lever;  
         [0021]    [0021]FIG. 5 is an enlarged cross-sectional view of a meltblowing nozzle constructed according to the invention;  
         [0022]    [0022]FIG. 6 is a cut-away elevated perspective view of a controlled fiberization nozzle constructed according to the invention;  
         [0023]    [0023]FIG. 7 is a bottom perspective view of the controlled fiberization nozzle of FIG. 6;  
         [0024]    [0024]FIG. 8 is a top view of the nozzle of FIGS. 6 and 7;  
         [0025]    [0025]FIG. 9 is a bottom perspective view of the meltblowing nozzle of FIG. 5;  
         [0026]    [0026]FIG. 10 is a top view of the meltblowing nozzle of FIGS. 5 and 9;  
         [0027]    [0027]FIG. 11 is a bottom perspective view of a bi-radial nozzle constructed according to the invention; and  
         [0028]    [0028]FIG. 12 is a top view of the bi-radial nozzle of FIG. 11. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    For purposes of this description, words of direction such as “upward”, “vertical”, “horizontal”, “right”, “left” and the like are applied in conjunction with the drawings for purposes of clarity. As is well known, liquid dispensing devices may be oriented in substantially any orientation, so these directional words should not be used to imply any particular absolute directions for an apparatus consistent with the invention.  
         [0030]    For purposes of simplifying the description of the present invention, the illustrative embodiment will hereinafter be described in relation to certain types of nozzles for distribution of thermoplastic liquid such as hot melt thermoplastic adhesives, but those of ordinary skill in the art will readily appreciate application of the present invention to dispensing of other materials and use other types of nozzles.  
         [0031]    With reference to the figures, and to FIGS. 1 and 1A in particular, a liquid dispensing system  10  for air assisted extrusion of liquid filaments is depicted as including a dispensing valve  12  and a manifold  14 . It will be appreciated that one or more of the die modules  12  may be mounted in side-by-side relationship to the manifold  14  that distributes liquid material and pressurized air to each of the die modules  12 . Each dispensing valve  12  includes a pneumatic valve mechanism  16  in a housing  18 . The pneumatic valve mechanism  16  is in fluid communication with the manifold  14  to receive the liquid material and to a liquid material flow passage  20  in the housing  18 . The valve may alternatively be electrically actuated for controlling flow of the liquid material through the dispensing valve  12 . A detailed description of the pneumatic valve mechanism  16  is provided in U.S. Pat. No. 6,056,155, entitled “Liquid Dispensing Device” and assigned to Nordson Corporation, the assignee of this invention. The disclosure of U.S. Pat. No. 6,056,155 is hereby incorporated herein by reference in its entirety.  
         [0032]    The housing  18  includes an air supply passage  22  adapted to receive the pressurized air from the manifold  14  and two air flow passages  24 ,  26  that are parallel to and on each side of the liquid material flow passage  20 . The pair of air flow passages  24 ,  26  allows mounting of different types of nozzles, but does result in different air flow path distances from the air supply passage  22 . Thus, an annular air chamber  28  in the housing  18  is in fluid communication with both the air supply passage  22  and the air flow passages  24 ,  26  for balancing air flow. The different types of nozzles  32   a,    32   b,    32   c  benefit from the even distribution of air flow. In the illustrative embodiments, these different types of nozzles  32   a,    32   b,    32   c  include meltblowing, controlled fiberization (hereinafter “swirl”) and nozzles currently manufactured and sold under the trademark SUMMIT™ by Nordson Corporation, the assignee of the present invention. The SUMMIT™ nozzles are hereinafter referred to as bi-radial nozzles.  
         [0033]    Portions of the dispensing valve  12  form a nozzle assembly  30  for selectively and expeditiously mounting various types of air assisted extrusion nozzles  32   a  to the housing  18 . In particular, the nozzle assembly  30  includes a clamping structure that allows access for removing and installing a nozzle  32   a  to the dispensing valve  12  from the front side opposite the manifold  14 . The nozzle  32   a  is frictionally held in contact with a nozzle mounting surface  36  by the opposition of a fixed member or wall  38  of the housing  18  and a positioning lever  40 , which creates a positioning and temporary clamping force parallel to the nozzle mounting surface  36 . The temporary support avoids prolonged manual holding of the nozzle  32   a,  which beneficially reduces the amount of time that a user must be in contact with the typically hot surface of the dispensing valve  12  as well as making installation more convenient. This frictional force from the positioning lever  40  advantageously supports the nozzle  32   a  while a pivoting clamping lever  42  locks the nozzle  32   a  to the nozzle mounting surface  36 . In particular, a socket head cap screw  44 , is threaded inward against housing  18 , outwardly pivoting an upper portion  46  of the clamping lever  42  about a pivot pin  48 , thereby pivoting a lower portion  50  of the clamping lever  42  under the nozzle  32   a.  Specifically, a cam surface  52  of the lower portion  50  makes inward and upward contact to a forward cam surface  54  of the nozzle  32   a,  with a rearward cam surface  56  of the nozzle  32   a  similarly supported by a cam surface  58  of the fixed member or wall  38 .  
         [0034]    As will be described in further detail below, different types of air assisted extrusion nozzles  32   a,    32   b,    32   c  may be selected for mounting to the nozzle assembly  30 . The air inputs  60 ,  62  and liquid input  64  of each nozzle  32   a,    32   b,    32   c  are registered to be in liquid communication respectively with the liquid material flow passage  20  and air flow passages  24 ,  26  of the housing  18 . Pressurized process air flow is diffused by one or more air troughs  66  that provide a tortuous air flow path through nozzle  32   a  and slow down the air flow velocity exiting process air discharge passages  68 .  
         [0035]    With reference to FIG. 2, the dispensing valve  12  is shown with the nozzle  32   a  and nozzle assembly  30  disassembled to illustrate additional features. The positioning lever  40  and clamping lever  42  are pivotally affixed to the housing  18  with the same pivot pin  48 . The positioning lever  40  resides within a slot  72  in the clamping lever  42  that allows the positioning lever  40  to pivot upward to an ejection position when the pivoting lever is in an unlocked or loosened state. The cap screw  44  is retained within a threaded hole  74  in the clamping lever  42  by a snap ring  76 . An upper surface  78  of the nozzle  32   a  includes a symmetric pattern of air inlets  60 ,  62  and liquid inlet  64  so that the nozzle  32   a  may be inserted in one of two orientations with one being 180 degrees rotated from the other. The upper surface  78  also includes symmetrically placed alignment recesses  86 ,  88  registered to receive an alignment pin  90  affixed to the nozzle mounting surface  36  (shown in FIGS. 1 and 1A), that assist in positioning the upper surface  78  relative to the nozzle mounting surface  36 .  
         [0036]    With reference to FIG. 3, the nozzle assembly  30  is shown with a bi-radial nozzle  32   a  mounted, as one type of air assisted extrusion. A detailed description of the bi-radial nozzle  32   a  is disclosed in co-pending U.S. Ser. No. 09/571,703, entitled “Module And Nozzle For Dispensing Controlled Patterns Of Liquid Material” and assigned to the common assignee, the disclosure of which is hereby incorporated herein by reference in its entirety. Shown in phantom, a meltblowing nozzle  32   b  and a swirl nozzle  32   c  are shaped similarly to the bi-radial nozzle  32   a  to be alternatively received in a recess  91  of the housing  18 .  
         [0037]    With reference to FIGS.  4 A- 4 C, use of the positioning lever  40  to assist in mounting and ejecting a nozzle  32   a  is illustrated with the clamping lever  42  adjusted to the unlocked position by outwardly adjusting the cap screw  44 . Thus, with reference to FIG. 4A, the cam surface  52  of the clamping lever  42  does not impede an uninstalled nozzle  32   a  moved upward into proximity to the nozzle mounting surface  36 , as depicted by the phantom lines. The rearward alignment recess  86  in the nozzle has sufficient dimensions to register to the alignment pin  90  with the nozzle shifted slightly forward to clear the fixed member or wall  38  which provides a rear boundary for recess  91 . If the positioning lever  40  is in the ejection position, further upward movement of the nozzle  32   a  will bear upon a projection  92  of the positioning lever  40 , pivoting the positioning lever  40  to an engaged position depicted in FIG. 4B. In particular, a cam surface  40   a  is brought into frictional contact with the forward surface  41  of the nozzle  32   a.  This urges the rearward cam surface  56  into engagement with cam surface  58  of the fixed member or wall  38  thereby forcing nozzle  32   a  against the nozzle mounting surface  36 . This temporarily aligns and clamps nozzle  32   a  within recess  91 . At this point, the clamping lever  42  may be moved to the locked position by tightening fastener  44  (shown best in FIG. 1A) for the period of use of the dispensing valve  12 . This urges cam surface  52  against cam surface  54  thereby urging nozzle  32   a  upwardly into a clamped, sealing engagement against mounting surface  36 .  
         [0038]    With reference to FIG. 4C, when the nozzle  32   a  requires repair or replacement with another nozzle, the clamping lever  42  is moved to the unlocked position as depicted. Then the positioning lever  40  is used as an ejection lever and is pivoted upward toward the ejection position. As the positioning lever  40  pivots upward, the projection  92  bears downward upon an upper cam surface  55  of the nozzle  32   a  for ejecting the nozzle  32   a.  A prying force thus applied by the positioning lever  40  on the nozzle  32   a  overcomes adhesion of accumulated liquid material during use.  
         [0039]    FIGS.  5 - 12  illustrate the three illustrative types of air assisted extrusion nozzles  32   a,    32   b,    32   c  adapted for being universally mounted to the dispensing valve  12 .  
         [0040]    With reference to FIGS.  6 - 8 , the controlled fiberization nozzle  32   c  has a circular air trough  94  that encompasses a central liquid input  96 . Each of the air jets  98  receives pressurized air from the two air flow passages  24 ,  26  of the housing  18  after being diffused and slowed down in the circular air trough  94  so that none of the air jets  98  directly receives the pressurized air. Consequently, the air flow is more uniform for all air jets  98 , as arrayed about a liquid orifice  100  that receives liquid material from the central liquid input  96 .  
         [0041]    With reference to FIGS. 5, 9 and  10 , the meltblowing nozzle  32   b  depicted in FIG. 2 is shown having a row of orifices  102  flanked by rows of air jets  104 . Balancing the air flow to these air jets  104  and providing consistent liquid flow to the orifices  102  is provided as shown in FIG. 10. The upper surface  78  of the nozzle  32   b  includes a central elongate slot  106  for communicating the liquid material from the liquid material flow passage  20  of the housing  18  to the length of the row of orifices  102 . Two elongate air troughs  108 ,  110  diffuse and slow down the air flow from each air flow passage  24 ,  26  respectively to the rows of air jets  104 .  
         [0042]    Similarly, with reference to FIGS. 11 and 12, the bi-radial nozzle  32   a  includes an elongate central slot  112  for providing liquid material to a row of orifices  70  and two elongate air troughs  66  to diffuse and slow down the air flow from each air flow passage  24 ,  26  respectively to the rows of air jets  68  nonradially positioned about the orifices  70 .  
         [0043]    By virtue of the foregoing, and in addition to other advantages a nozzle assembly  30  for a dispensing valve  12  of a liquid dispensing system  10  is readily reconfigurable for various types of air assisted extrusion nozzles  32   a,    32   b,    32   c  without having to disassemble the dispensing valve  12  from the manifold  14  or having to remove multiple fasteners.  
         [0044]    While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments has been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The various features of the invention may be used alone or in numerous combinations depending on the needs and preferences of the user. This has been a description of the present invention, along with the preferred methods of practicing the present invention as currently known. However, the invention itself should only be defined by the appended claims, wherein we claim: