Patent Publication Number: US-6981656-B2

Title: Quick cleaning hot melt adhesive dispensing apparatus

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to thermoplastic material dispensing apparatus and, more particularly, dispensing apparatus configured to be easily cleanable particularly when used for dispensing certain problematic hot melt adhesive materials, such as polyurethane reactive (PUR) adhesives. 
   BACKGROUND OF THE INVENTION 
   Hot melt adhesives are typically thermoplastic adhesives that are solid at room temperature and melted prior to use. Hot melt adhesives may be used during such diverse activities such as building construction, shoe manufacture, and book binding. In addition, many uses exist in the assembly of automobile parts, electronics, electrical equipment, appliances, electrical components, furniture and other widely ranging manufacturing processes. The common forms of hot melt adhesives include, for example, polyamide adhesives, pressure sensitive adhesives (PSA), ethylene vinyl acetate (EVA), polyurethane reactive (PUR) adhesives, and other types of adhesives. The present invention is especially applicable to PUR adhesives, however, its various aspects are applicable to other types of meltable thermoplastic materials as used in many circumstances, such as those mentioned above. 
   Clean up and maintenance procedures of adhesive dispensing systems are always important considerations in a manufacturing environment. PUR adhesives present additional problems and challenges in that these adhesives are moisture curable and are generally not easily cleaned or flushed from a dispensing system having a large number of small precision parts and passages. Thus, dispensing systems are especially difficult to clean and maintain when used with PUR hot melts and are therefore more likely to require increased down time and maintenance. This results in higher manufacturing costs. 
   Various components in an adhesive dispensing system will require cleaning and maintenance including adhesive distribution bodies such as the manifold or service block associated with a dispensing apparatus. Such an apparatus typically includes at least one dispensing module having an internal valve element for selectively opening and closing a discharge passage and thereby either allowing or preventing the discharge of adhesive in a desired manner. The module is often operated pneumatically, although electrically operated modules also exist. At least one module is mounted to a manifold or service block which supplies at least the molten hot melt adhesive to the valve module and, if pneumatically operated, may also supply air for operating the valve element within the module. In addition, if the valve module utilizes process air, for example, to produce a particular adhesive spray pattern, the process air may also be provided through the manifold or service block. 
   In view of the current challenges associated with cleaning and maintaining apparatus for dispensing thermoplastic material, it would be desirable to provide such apparatus, including service blocks, manifolds or other material distribution bodies in the dispensing system, with more easily cleanable and/or maintainable material supply and distribution passages in order to decrease cleaning and maintenance costs and the downtime associated with these procedures. 
   SUMMARY OF THE INVENTION 
   In one aspect, the present invention provides an apparatus for dispensing thermoplastic material which is configured for easy cleaning and maintenance procedures to address residual material in the apparatus. The apparatus generally comprises a distribution body having an interior space and a removable insert contained in the interior space. The interior space may be a throughbore in the distribution body or it may be another configuration of passage which may or may not be part of a network of passages in the distribution body. The removable insert includes one or more flow passages for providing thermoplastic material to a dispensing element, such as a valve module and may be easily removed for cleaning, maintenance, or replacement purposes. As one example, the removable insert can extend from one side of the distribution body at which it connects to a supply of the thermoplastic material to an opposite side of the distribution body where it connects, for example, to the valve module. The first end of the removable insert can include a fitting for connecting to a thermoplastic material supply conduit and the opposite end or second end can include a seal which is configured to contact the valve module and prevent leakage of the thermoplastic material. As one alternative, the insert may comprise a tubular network for disposition in a manifold. 
   In another aspect of the invention, the distribution body is comprised of at least two pieces which mate together along a flow passage and which may be separated to assist with cleaning and maintenance procedures associated with that flow passage. The flow passage itself may supply the thermoplastic material to the valve module or other dispensing element. Alternatively, the flow passage may receive the removable insert discussed above. In either instance, the split configuration of the distribution body allows for easier and quicker cleaning and maintenance procedures. 
   The invention further contemplates methods of operating thermoplastic material dispensing apparatus. According to one method, thermoplastic material is supplied to a dispensing element from a pressurized supply of the thermoplastic material through a flow passage in a tubular insert carried by a distribution body. Thermoplastic material is discharged from the dispensing element and then stopped. The flow passage of the tubular insert is depressurized and then the tubular insert is removed from the distribution body. The flow passage of the tubular insert is then cleaned or the tubular insert itself is replaced by another tubular insert prior to resuming use of the dispensing apparatus. 
   In accordance with another method of the invention, the material distribution body is comprised of at least first and second pieces which mate together along the length of a flow passage. The method generally involves the steps outlined above for the first embodiment, except that to facilitate quicker and easier cleaning, the first and second pieces of the distribution body are disconnected from one another after depressurizing at least that portion of the dispensing apparatus or system. The pieces need not be completely decoupled from each other but merely disconnected enough to facilitate access to portions of the flow passage. This flow passage along which the distribution body is split or disconnected may or may not also include a removable hollow or tubular insert which actually carries the thermoplastic material during operation. In either case, the method facilitates quicker and more effective cleaning and maintenance procedures. 
   These and other objects, advantages, and features of the invention will become more readily apparent from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational view of a dispensing apparatus constructed in accordance with one embodiment of the invention. 
       FIG. 2  is a cross sectional view taken along line  2 — 2  of  FIG. 1 . 
       FIG. 3A  is a perspective view of the removable insert shown in  FIG. 2 . 
       FIG. 3B  is a perspective view from the opposite side of the insert shown in  FIG. 3A . 
       FIG. 4  is a side elevational view of a dispensing apparatus constructed in accordance with another embodiment of the invention. 
       FIG. 5  is an exploded perspective view of the service block illustrated in  FIG. 4 . 
       FIG. 6  is an exploded perspective view of a service block constructed in accordance with another embodiment. 
       FIG. 7  is a cross sectional view similar to  FIG. 2 , but illustrating an alternative service block. 
       FIG. 8  is a fragmented view of an alternative tubular inserted constructed according to the invention. 
       FIG. 9  is a fragmented view of a manifold section configured to receive the tubular insert of  FIG. 8 . 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 ,  2  and  3 A– 3 B illustrate a dispensing apparatus  10  comprised of a dispensing module  12  coupled to a liquid distribution body  14  by fasteners  16 . The distribution bodies disclosed herein may be service blocks, manifolds, or other types of liquid distribution bodies having one or more passages for distributing liquid to a dispenser. A mounting block  18  is connected to service block  14  by fasteners  20  and may be releasably coupled to a mounting rod (not shown) using fasteners  22  to clamp block portions  18   a ,  18   b  around the mounting rod (not shown) which is received in a hole or throughbore  24 . A thermoplastic material inlet  30  is provided in a fluid fitting  32  secured to service block  14  by turning a hex portion  34 . An electric cable  36  supplies power to a heater (not shown) and RTD (not shown) within service block  14 . Apparatus  10  is therefore generally similar to the one shown in U.S. Pat. No. 4,785,996, assigned to the assignee of the present invention, and the disclosure of which is incorporated herein by reference. Fitting  32  is coupled to an insert  40  which is received in a removable fashion within service block  14  in accordance with one aspect of the invention. Thermoplastic material, such as a PUR hot melt adhesive or another type of hot melt adhesive, may be introduced through inlet  30  and respective passages  42 ,  44  in fitting  32  and removable insert  40 . The material then enters an inlet port  46  in module  12  and an internal module passage or passages  48 . The material will discharge from an outlet  50  of a nozzle  52  when a reciprocating valve element  54  is moved upwardly from the closed position shown in  FIG. 2  to an open position. Removable insert  40  is sealed against module  12  by an O-ring  56  or by another suitable sealing method. Insert  40  may be removed from service block  14  by uncoupling module  12  and service block  14  and removing nut  34 . If necessary, fitting  32  and O-ring  56  may be removed, respectively, from internal threads  60  and annular recess  64  of flange  62 . In this manner, insert  40  may be quickly and effectively cleaned of any residual adhesive within material passage  44  and elsewhere on insert  40  and then insert  40  may be replaced within surface block  14 . Alternatively, insert  40  may be replaced by a different insert. 
     FIGS. 4 and 5 ,  FIG. 6 , and  FIG. 7  respectfully illustrate three alternative embodiments of the invention in which like elements with the first embodiment described above are indicated using like reference numerals. These identical components therefore need not be described again. Modified components are indicated below by like reference numerals with prime marks (′), double prime marks (″) or triple prime marks (′″). The embodiment of  FIGS. 4 and 5  does not use the removable insert  40  described in connection with the first embodiment. Instead, to allow for easy cleaning and maintenance, service block  14 ′ is comprised of at least two component parts  14   a ,  14   b  which may be separated to expose portions of a thermoplastic material inlet or flow passage  70   a ,  70   b . Thus, when cleaning and maintenance is necessary, fasteners  72  may be removed from threaded holes  72   a  to separate service block portions  14   a  and  14   b  to fully expose inlet passage portions  70   a ,  70   b  for easy cleaning. 
     FIG. 6  illustrates another embodiment similar to  FIGS. 4 and 5 , except that fasteners  72  retain a lower portion  14   c  of service block  14 ″ to an upper service block portion  14   d . The two portions  14   c ,  14   d  are easily separated from one another to again expose the entire length of the material inlet or flow passage portions  70   c ,  70   d.    
     FIG. 7  is a cross sectional view similar to  FIG. 2 , but illustrating a dispensing apparatus  10 ′″ which essentially combines the features of a removable insert and a separate material distribution body. It will be appreciated that with the combination of a separable service block  14 ′″ having portions  14   a ,  14   b  ( FIG. 5 ) and a removable insert  40 , it will be easier in various situations to access and remove insert  40  for cleaning and/or replacement purposes. In this regard, service block portion  14   b  may be removed as shown in  FIG. 7  and fasteners  16  may simply be loosened to allow insert  40  to be removed from service block portion  14   a  and then cleaned or replaced as necessary. 
     FIGS. 8 and 9  illustrate an alternative embodiment of the invention in which a tubular insert  100  may be removably affixed within a manifold  110 . Specifically, insert  100  is shown in  FIG. 8  and includes interconnected tubular sections  102 ,  104 ,  106   a–d . These tubular sections  102 ,  104 ,  106   a–d  may contain interconnected flow passages for various uses, such as for directing flow to one or more dispensers, directing flow through a filter, or providing system drainage. As with the previous embodiments, the various sections may be threaded and/or coupled to suitable fittings appropriate for their intended use. Tubular insert  100  is removably receivable within a manifold  110  ( FIG. 9 ) having interior spaces or passages  112 ,  114 ,  116   a–d  which are sized and shaped to receive sections  102 ,  104 ,  106   a–d  of insert  100 . Manifold  110  includes another half (not shown) which may be secured in place using fasteners in screw holes  120  after insert  100  is received within passages or spaces  112 ,  114 ,  116   a–d.    
   While the present invention has been illustrated by a description of a preferred embodiment and while this embodiment has been described in some detail, it is not the intention of the Applicants 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.