Abstract:
A nozzle for a liquid dispenser that incorporates a cleaning probe capable of removing foreign debris from a nozzle discharge passageway. The cleaning probe is moveable between a retracted position that permits fluid flow to a discharge orifice terminating the discharge passageway and an extended position in which the cleaning probe extends into the discharge passageway. As the cleaning fixture advances from the retracted position to the extended position, foreign debris present in the discharge passageway is displaced and ejected out of the discharge orifice.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention generally relates to liquid dispensing apparatus and methods and, more particularly, to nozzles for liquid dispensing modules having a need to be cleaned of debris which may collect and cause clogging.  
         BACKGROUND OF THE INVENTION  
         [0002]    Liquid dispensing systems are incorporated into many manufacturing production lines for dispensing a liquid onto a substrate. Certain liquid dispensing systems are configured for applying a pattern of a heated liquid, such as a thermoplastic material or a hot melt adhesive, to a continuously-moving substrate, such as a woven or non-woven web used in the manufacture of multilayer diapers and other multilayer hygienic products. To that end, liquid dispensing systems include one or more discharge passageways arranged to provide the pattern. Typically, the discharge passageways are located in corresponding nozzles removably attached directly or indirectly to a liquid distribution manifold. The flow of liquid from a liquid supply to the nozzle may be interrupted by a valve element of an intervening dispensing module for dispensing the liquid with a pattern.  
           [0003]    Particles may be present in the liquid being dispensed from the discharge passageway. For example, liquids in hot melt adhesive dispensing may include solidified, insoluble particles or char produced by operation of a melter providing the hot melt adhesive to the liquid dispensing system. Relatively small particles pass through the discharge passageway and are dispensed along with the liquid. Relatively large particles may become lodged in the discharge passageway and produce clogs. As a result, the discharge passageway is susceptible to partial or total obstruction by foreign debris that either reduces or prohibits liquid flow to the discharge orifice. Flow restriction may also arise from solidified liquid coating the wall surrounding the discharge passageway. Yet another source of particles is debris originating from solidified liquid residue produced during non-operational intervals, such as maintenance periods. This can adversely affect adhesive bonding and reduce product quality.  
           [0004]    Conventionally, clogged discharge passageways in a nozzle are cleaned by halting the flow of product in the production line and removing the clogged nozzle from the liquid dispensing system. The clogged nozzle is disassembled and the discharge passageway is cleaned of debris. The reassembled nozzle is reintroduced into the adhesive dispensing system, adjusted and calibrated. The production line is then restarted. The cleaning process is time consuming and labor intensive. Moreover, because the production line is stopped to clean the nozzle, the process throughput is reduced.  
           [0005]    What is needed, therefore, is a liquid dispensing system in which the discharge passageway of a nozzle can be cleared of obstructions without removing the nozzle from the dispensing system.  
         SUMMARY OF INVENTION  
         [0006]    The present invention provides a nozzle that includes a coupling member, and a nozzle body capable of being coupled mechanically by the coupling member with the liquid dispenser. The nozzle body has a discharge passageway adapted to be coupled in fluid communication with a liquid supply passageway of a liquid dispenser. The nozzle further includes a cleaning probe moveable between a retracted position in which liquid flows through the discharge passageway of the nozzle body and an extended position in which the cleaning probe extends into the discharge passageway. When the cleaning probe is moved from the retracted position to the extended position, foreign debris in the discharge passageway is ejected from the discharge orifice.  
           [0007]    The present invention also provides a method of operating a thermoplastic material dispenser capable of dispensing thermoplastic material through a discharge passageway in a nozzle. The method includes extending a cleaning probe integral with a nozzle to an extended position within the discharge passageway and retracting the cleaning probe from the extended position to a retracted position withdrawn from the discharge passageway.  
           [0008]    According to the principles of the invention, the discharge passageway in a dispenser nozzle may be cleaned frequently, while minimizing idle production time required for performing the cleaning. Frequent cleaning of the discharge passageway at periodic intervals increases the product quality by minimizing the occurrence of clogs. The ability to rapidly clean the discharge passageway without removing the nozzle from the liquid dispenser reduces the down time of the production line, which also increases throughput and decreases cost. The discharge passageway may be cleaned periodically according to a preventative maintenance schedule or upon the observation of a clogged discharge passageway.  
           [0009]    Various additional advantages 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 taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]    [0010]FIG. 1 is a side elevational view of a liquid dispensing module and a nozzle attached to the liquid dispensing module;  
         [0011]    [0011]FIG. 2A is a cross-sectional view of the nozzle of FIG. 1;  
         [0012]    [0012]FIG. 2B is a cross-sectional view similar to FIG. 2A in which the cleaning probe is extended into the discharge passageway of the nozzle;  
         [0013]    [0013]FIG. 3 is a front elevational view of the cleaning fixture; and  
         [0014]    [0014]FIG. 4 is an end view of an alternative embodiment of the cleaning fixture. 
     
    
     DETAILED DESCRIPTION  
       [0015]    With reference to FIG. 1, a liquid dispensing system  10  for dispensing liquids, such as thermoplastic materials and hot melt adhesives, generally includes a gun body  12  and a dispenser module  14  mounted to the gun body  12 . The gun body  12  is provided with a mounting bracket  16  mountable to a suitable support structure (not shown), a hose port  18  for connection of a fluid line to supply liquid, and a cord set  20  that provides electrical connections. Dispenser module  14  may be any suitable flow control device adapted receive and dispense liquid. Typically, dispenser module  14  is configured with a valve assembly that is actuated between an open position for dispensing liquid and a closed position in which the flow of liquid is discontinued. The invention contemplates that the dispenser module  14  may be any liquid distribution manifold or device that may or may not include valve assemblies and that has liquid passageways for providing liquid to one or more nozzles.  
         [0016]    With reference to FIGS. 1, 2A,  2 B and  3 , dispenser module  14  is provided with a nozzle  22  that includes a nozzle body  24  and an internally-threaded coupling member or connector nut  26 . Connector nut  26  couples the nozzle body  24  to an externally-threaded adapter  28  extending from one end of dispenser module  14 . Connector nut  26  has faceted portions  30  capable of being engaged by a tool, such as by the jaws of a wrench, for tightening the threaded engagement between nozzle body  24  and dispenser module  14 . Nozzle  22  is interchangeable with other nozzles supporting discharge orifices of different diameters.  
         [0017]    Provided in the nozzle body  24  is a passageway  34  that receives liquid supplied from a passageway  36  in the dispensing module  14 . Passageway  34  extends along a longitudinal axis  37  and intersects a longitudinal axis  38  of a passageway  40  for defining a fluid path in the nozzle body  24 . The dispensing module  14  includes a valve element  41  that is movable relative to a valve seat  43  located in passageway  36  for regulating the flow of liquid into passageway  34  and subsequently into passageway  40 . Specifically, the valve element  41  makes a highly effective positive sealing contact along a continuous line of contact with the valve seat  43  for interrupting the flow of liquid from passageway  36  to passageway  34 .  
         [0018]    Positioned within passageway  40  is a nozzle insert  42  having a discharge passageway  44  terminated by a discharge orifice  46 . Insert  42  is retained in place in a suitable manner, such as by ramping a surrounding area of nozzle body portion  43  as shown in FIGS. 2A and 2B. Discharge passageway  44  has the smallest diameter of any of the passageways  34 ,  40 ,  44  in nozzle  22 , so that discharge passageway  44  is a likely location in the fluid path for trapping of foreign debris present in the liquid. The nozzle insert  42  is positioned such that discharge passageway  44  is substantially aligned with the longitudinal axis  38 . Liquid flowing through the fluid path consisting of the interconnected passageways  34 ,  40 ,  44  is discharged from the nozzle  22  through discharge orifice  46 . A planar sealing surface  48  of nozzle body  24  engages a confronting planar sealing surface  49  of adapter  28  to provide a substantially fluid-tight, face-to-face mounting of nozzle  22  to liquid dispenser  14 . The nozzle body  24  may optionally be rotatable relative to the dispenser module  14  without rotating or otherwise loosening connector nut  26 .  
         [0019]    With continued reference to FIGS. 1, 2A,  2 B and  3 , nozzle  22  further includes a cleaning fixture  50  having a cleaning pin or probe  56  movable between retracted and extended positions for clearing foreign debris from the discharge passageway  44  in nozzle insert  42 . A major axis or length of the cleaning probe  56  is aligned substantially parallel with longitudinal axis  38  of discharge passageway  44  so that a leading tip  53  of the cleaning probe  56  may enter discharge passageway  44  when moved from the retracted position to the extended position. Cleaning probe  56  occupies a small volume of supply passageway  34  when in the retracted position, which minimizes any obstruction to the flow of thermoplastic material to the discharge passageway  44 .  
         [0020]    The cleaning probe  56  is characterized by a diameter measured radially relative to its length. Typically, the diameter of cleaning probe  56  is uniform along its length, although the invention is not so limited. The diameter of the cleaning probe  56  is slightly less than a diameter of the discharge passageway  44 , measured radially relative to the longitudinal axis  38  to the cylindrical, inwardly-facing surface surrounding passageway  44 . The dimensional difference provides a clearance sufficient for the leading tip  53  of cleaning probe  56  to enter and extend through the discharge passageway  44 . The cleaning probe  56  may be, for example, formed from a short length of wire or rod. The leading tip  53  may be blunt, as shown in FIGS. 1-3 or may have a different configuration, such as tapering to a point.  
         [0021]    A threaded portion  58  of cleaning fixture  50  is engaged with a threaded portion  60  of a bushing  52  sealingly engaged with passageway  40 . Bushing  52  is fixed within body  24  in a suitable manner, such as by brazing. The mated threaded portions  58 ,  60  cooperate for guiding the cleaning probe  56  axially along longitudinal axis  38  toward the discharge passageway  44 . A rotating driving element  54  is used to apply a torque for turning threaded portion  58  relative to stationary threaded portion  60  in one rotational direction to advance the cleaning probe  56  from the retracted position to the extended position. To withdraw the cleaning probe  56  from the extended position to the retracted position, a force is applied to driving element  54  that turns threaded portion  58  in an opposite rotational direction relative to the threaded portion  60 . A handle  55  provides an angled arm for applying a rotational force to the cleaning fixture  50 . Alternatively, handle  55  may be a wheel or a knob configured to facilitate manual rotation. In a broader sense, driving element  54  is a reciprocating element since it achieves the necessary back and forth motion. Such reciprocating movement could be achieved in other manners as well, including manners that do not require rotation. Also, it will be appreciated that element  54  may be integral or separate from the remainder of fixture  50 .  
         [0022]    With reference to FIGS. 2A, 2B and  3 , the cleaning fixture  50  further includes a trailing shoulder  62  adapted to contact a seating surface  64  of bushing  52  when the cleaning probe  56  is retracted, as shown in FIG. 2A, so as to provide a fluid seal and a positive stop in the retracted position. A leading shoulder  68  of cleaning fixture  50  contacts a seating surface  66  provided in discharge passageway  44  so as to provide a positive stop in the extended position, as shown in FIG. 2B. The seating surfaces  64 ,  66  effectively limit the axial movement of the cleaning probe  56  along the longitudinal axis  38  and prevent fluid loss from passageway  40  in the retracted position. The shoulders  62 ,  68  and the seating surfaces  64 ,  66  are illustrated as being frustoconical in shape with complementary inclination angles, although the invention is not so limited. A cylindrical portion  70  positioned between shoulders  62 ,  68  has a diameter similar to the diameter of an unthreaded portion  72  of the bushing  52 . Sliding contact between portions  70  and  72  assists in guiding the cleaning probe  56  toward the discharge passageway  44 .  
         [0023]    Although passageways  34  and  40  are depicted as intersecting perpendicularly, the invention is not so limited. The relative inclination of passageways  34  and  40  is constrained only by the ability to access the driving element  54  of cleaning fixture  50  from the exterior of the nozzle housing  24 .  
         [0024]    In use and with reference to FIGS. 1, 2A,  2 B and  3 , liquid is dispensed from discharge orifice  42  and the cleaning fixture  50  is parked in the retracted position with cleaning probe  56  located within passageway  44 . If the flow of liquid from the discharge orifice  46  of nozzle  22  is perceived to be reduced or at regular maintenance intervals, the cleaning probe  52  is advanced from the retracted position to the extended position so that the cleaning probe  52  enters discharge passageway  44  and travels toward the discharge orifice  42 . Movement of cleaning probe  52  in this direction causes the leading tip  53  to displace or move any foreign debris, such as char, present in the discharge passageway  44  toward the discharge orifice  42 . The axial dimension or length of cleaning probe  52  is selected so that the leading tip  53  projects out of the discharge orifice  42 , when in the extended position, by a distance effective for ejecting foreign debris from discharge passageway  43 . After the discharge passageway  43  is cleared, the cleaning probe  52  is returned to the retracted position in passageway  40  and the dispensing of liquid from discharge orifice  42  may be resumed.  
         [0025]    With reference to FIG. 4 in which like reference numerals refer to like features in FIGS. 1, 2A,  2 B and  3 , the driving element  54  of a cleaning fixture  50   a  may carry a drive recess  57 , such as a cross slot or a hex head. The drive recess  57  is capable of being engaged by a correspondingly shaped end of a driving tool or implement (not shown), such as a slotted-type screwdriver, a wrench or a drive socket, for rotating the driving element  54  to move the cleaning probe  56  between the retracted and extended positions.  
         [0026]    While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in considerable detail in order to describe the best mode of practicing the invention, it is not the intention of applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the spirit and scope of the invention will readily appear to those skilled in the art. The invention itself should only be defined by the appended claims, wherein I claim: