Abstract:
A modular applicator for dispensing liquid including a plurality of manifold segments, a plurality of removable pumps, and a drive motor coupled to each pump. The manifold segments are coupled in side-by-side relation and each includes a liquid supply passage and a liquid discharge passage. Each pump includes an inlet communicating with the liquid supply passage, an outlet communicating with the liquid discharge passage and a pumping mechanism for pumping the liquid from the inlet to the outlet. The drive motor is coupled to each pump to simultaneously operate each pumping mechanism and dispense the liquid from a plurality of dispensing modules coupled with each manifold segment. The dispensing modules are recirculating modules which direct the liquid back into the corresponding manifold segment when they are in closed positions.

Description:
This is a continuation-in-part application of U.S. application Ser. No. 09/141,959, filed Aug. 28, 1998 (pending) which is a continuation-in-part of U.S. application Ser. No. 09/063,651, filed Apr. 20, 1998 (abandoned). The disclosures of these two related patent applications are hereby fully incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to applicators or fiberization dies for applying thermoplastic materials to a substrate or for producing nonwoven materials. 
     BACKGROUND OF THE INVENTION 
     Thermoplastic materials, such as hot melt adhesive, are dispensed and used in a variety of situations including the manufacture of diapers, sanitary napkins, surgical drapes as well as many others. This technology has evolved from the application of linear beads or fibers of material and other spray patterns, to air-assisted applications, such as spiral and meltblown depositions of fibrous material. 
     Often, the applicators will include one or more dispensing modules for applying the intended deposition pattern. Many of these modules include valve components to operate in an on/off fashion. One example of a dispensing module is disclosed in U.S. Pat. No. 6,089,413, assigned to the assignee of the present invention, and the disclosure of which is hereby fully incorporated by reference herein. This module includes valve structure which changes the module between ON and OFF conditions relative to the dispensed material. In the OFF condition, the module enters a recirculating mode. In the recirculating mode, the module redirects the pressurized material from the liquid material inlet of the module to a recirculation outlet which, for example, leads back into a supply manifold and prevents the material from stagnating. Many other modules or valves have also been used to provide selective metering and/or on/off control of material deposition. 
     Various dies or applicators have also been developed to provide the user with some flexibility in dispensing material from a series of modules. For short lengths, only a few dispensing modules are mounted to an integral manifold block. Longer applicators may be assembled by adding additional modules to the manifold. Additional flexibility may be provided by using different die tips or nozzles on the modules to permit a variety of deposition patterns across the applicator as well. The most common types of air-assisted dies or nozzles include meltblowing dies, spiral nozzles, and spray nozzles. Pressurized air used to either draw down or attenuate the fiber diameter in a meltblowing application, or to produce a particular deposition pattern, is referred to as process air. When using hot melt adhesives, or other heated thermoplastic materials, the process air is typically also heated so that the process air does not substantially cool the thermoplastic material prior to deposition of the material on the substrate or carrier. Therefore, the manifold or manifolds used in the past to direct both thermoplastic material and process air to the module include heating devices for bringing both the thermoplastic material and process air to an appropriate application temperature. 
     In the above-incorporated patent applications, various embodiments of modular applicators are disclosed which allow a user to more easily configure the applicator according to their needs. Generally, these applicators include a plurality of manifold segments disposed in side-by-side relation, with each manifold segment including a dispensing module or valve and a positive displacement pump. Material, such as hot melt adhesive, flows through the side-by-side manifold segments to each pump. The pumps individually direct the material to each corresponding dispensing module. Heated process air is also directed through each manifold segment to the die tip or nozzle of the module and impacts the dispensed material to achieve a desired effect on the deposition pattern. A separate recirculating module is provided so that the material discharged from the pump flows to the recirculation module if the fiberization die module is shut off or closed. The recirculated flow ensures that flow through the pump is uninterrupted. These related applications disclose applicators having a single integral drive shaft extending through side-by-side positive displacement gear pumps or, alternatively, a segmented drive shaft which allows the manifold segments to be removed or added without the need for disassembling the entire manifold. In each case, the number of manifold segments and modules define the effective dispensing length of the applicator. 
     Despite the various progress made in the technology, there is still a need to increase the speed and efficiency at which an applicator may be configured and maintained or repaired. There is also a continuing desire to reduce the cost and complexity associated with these applicators. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides a modular applicator for dispensing liquid including a plurality of manifold segments coupled in side-by-side relation. Each manifold segment includes a liquid supply passage and a liquid discharge passage. A plurality of pumps are respectively mounted in a removable manner to the plurality of manifold segments. Each of the pumps includes an inlet communicating with the liquid supply passage of the corresponding manifold segment, an outlet communicating with the liquid discharge passage of the corresponding manifold segment and a pumping mechanism for pumping the liquid from the inlet to the outlet. A drive motor is coupled to each of the pumps for operating each of the associated pumping mechanisms. 
     More specifically, the plurality of pumps are preferably gear pumps with one of the gears being a drive gear. A shaft is coupled between the drive motor and each of the drive gears to simultaneously operate each of the pumps. The system further includes a plurality of on/off dispensing modules respectively coupled with the manifold segments. These dispensing modules may be pneumatically operated valves and, for operational purposes, the manifold segments include air distribution passages for delivering pressurized control air to each of the pneumatically operated valves. An air control valve may be mounted to one or more of the manifold segments to selectively supply the pressurized control air to an associated one or more of the pneumatically operated valves. The manifold segments further include liquid distribution passages for delivering the liquid from one of the manifold segments to another of the manifold segments through opposed side surfaces thereof. Likewise, process air distribution passages also communicate between adjacent manifold segments for supplying heated process air to each of the modules. A pair of heating rods extend through each of the manifold segments for heating liquid and process air sections thereof. The liquid and process air sections of each manifold segment are thermally separated by one or more insulators, such as slots and/or bores. 
     The dispensing modules are preferably recirculating modules and appropriate passages are provided in each associated manifold segment to ensure that liquid is recirculated back into the manifold segment if the module is in an OFF position. The preferred liquid dispensing system also has the advantage that the pumps may be removed from the manifold segment without decoupling the manifold segments from one another. In this regard, the common drive shaft may be disengaged from one or more pumps by pulling the drive shaft out of one end of the manifold and, once disengaged, the appropriate pump or pumps may be removed and either repaired or replaced as necessary. 
     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 THE DRAWINGS 
     FIG. 1 is a partially exploded perspective view illustrating the preferred dispensing applicator of the present invention. 
     FIG. 2 is an exploded perspective view showing the end plates of the manifold assembly. 
     FIG. 3 is a partially exploded perspective view showing one of the gear pumps. 
     FIG. 4 is an exploded perspective view illustrating a first manifold segment. 
     FIG. 5 is an exploded perspective view illustrating a second manifold segment. 
     FIG. 6 is a perspective view of a gasket positioned between one of the manifold segments and a corresponding one of the air control valves. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a preferred applicator constructed in accordance with the inventive concepts. Applicator  10  includes a dispensing assembly  12  comprised of individual side-by-side manifold segments  14 , dispensing modules  16 , air control valves  18  and gear pumps  20 . In general, a pressurized liquid is introduced into manifold segments  14  and is metered by gear pumps  20  individually associated with each manifold segment  14  to each corresponding dispensing module  16 . Air control valves  18  selectively supply pressurized control air through the attached manifold segment  14  to the corresponding module  16  to operate module  16  between open and closed (ON and OFF) positions. Dispensing module  16  is preferably a recirculating module, such as the module disclosed in U.S. Pat. No. 6,089,413 incorporated above. 
     In the illustrated embodiment of applicator  10 , each manifold segment  14  includes an identical dispensing module  16 , air control valve  18 , which may be a conventional spool operated solenoid valve, and gear pump  20 . From the description to follow, it will be appreciated that the plurality of dispensing modules may be controlled by less than a corresponding number of air control valves  18 . Also, one or more gear pumps  20  may be removed and replaced with a substitution block (not shown) which diverts liquid material back into the corresponding manifold segment  14  and does not direct the liquid material into a corresponding dispensing module  16 . Thus, dispensing assembly  12  may be configured in many different manners depending on the application needs and desires of the user. Except as noted herein, each assembly comprised of a manifold segment  14 , a dispensing module  16 , an air control valve  18  and a gear pump  20  is preferably identical. 
     As further shown in FIG. 1, dispensing assembly  12  includes a pair of end plates  30 ,  32  sandwiching the dispensing portion of assembly  12  therebetween. A DC servo motor  34  and conventional right angle gear box  36  are provided to simultaneously drive each gear pump  20  coupled with manifold segments  14 . A filter block  40  is secured to end plate  30  and contains a removable filter element (not shown) accessible by turning a handle  42  coupled with a threaded cap  44 . The filter element within block  40  filters liquid material introduced through an input  50  before directing that material through end plate  30  and into the adjacent manifold segment  14  for distribution to each gear pump  20  and ultimately each module  16 . Filter block  40  includes a pre-filter transducer port  52  and a post-filter transducer port  54 . These ports  52 ,  54  allow pressure transducers to be coupled upstream and downstream of the filter element to allow measurement of the pressure differential and thereby allow detection of a clogged filter condition which necessitates cleaning or replacement. A pressure relief valve  56  is provided to relieve liquid pressure within dispensing assembly  12  during, for example, maintenance and repair. A pair of cordsets  60 ,  62  and corresponding heater rods  60   a ,  62   a  are provided to respectively heat the process air section and liquid section of each manifold segment  14 . Rods  60   a ,  62   a  are respectively inserted through holes  64  and  66  in end plate  30  and holes  67 ,  69  which align in each manifold segment  14 . A plug  70  is threaded into one side of the liquid supply passage in filter block  40  with the other side aligning with the liquid supply passage of the adjacent manifold segment  14  as will be discussed below. Fasteners  74  couple filter block  40  to end plate  30 . 
     Referring to FIG. 2, end plates  30 ,  32  are shown in greater detail with certain components illustrated in exploded view for clarity. Each end plate  30 ,  32  includes a control air input port  82 ,  84  and a pair of control air exhaust ports  86 ,  88  and  92 ,  94  which receive threaded exhaust filters  96 ,  98  and  102 ,  104 . Port  84  includes a plug  106 , although it will be appreciated that this supply port  84  may instead include an input fitting  108  as shown with the opposite end plate  30 , depending on the needs of the user. A supply port  84   a  and exhaust ports  92   a ,  94   a  communicate with the control air input  84  and exhaust ports  92 ,  94  in the top of each end plate as shown in end plate  32 . In addition, two additional ports  107 ,  109  are provided on the inside facing surface of each end plate and are used to direct control air to the adjacent manifold segment as will be described below. Each end plate  30 ,  32  also includes a plurality of threaded fastener holes  110  and counterbored fastener receiving holes  112 . Fasteners  114  are used to secure the respective end plate  30 ,  32  to the adjacent manifold segment  14  (FIG.  1 ). 
     Process air is supplied into either of the end plates  30 ,  32  through a bore  120  or  122 . The other bore is plugged. The bores  120 , 122  lead to a process air slot  124  as shown on inner face  32   a  of plate  32 . Although not shown, plate  30  has the same slot on its inner face. Process air therefore supplied to slot  124  and this slot  124  communicates with a series of radially spaced bores  126  in each manifold segment  14  surrounding the process air heating rod  60   a  (FIG.  1 ). Each slot  126  redirects air in a serpentine fashion through the bores  126  such that it is uniformly heated as it traverses back-and-forth along the length of the connected manifold segments  14  and heater rod  60   a . Another slot  128  also directs the process air in this serpentine fashion. The final bore  126  in the serpentine air flow path communicates with a slot  130  which leads to an air supply passage  132 . The air supply passage  132  extends through each of the connected manifold segments  14  and a perpendicular bore  136  in each manifold segment  14  communicates with the corresponding module  16  to provide the process air to the nozzle region  16   a.    
     A liquid material input passage  140  communicates with the liquid supply passage of filter block  40  and with the respective inputs of the manifold segments in a serial fashion as will be discussed below. The input port  142  in the opposite end plate  30  is plugged. A cover plate  150  is attached to each end plate  30 ,  32  with each plate  150  secured by sets of fasteners  152  and sealed by an O-ring  154 . Only the cover plate  150  associated with end plate  32  is shown in FIG. 2 for clarity although it will be appreciated that an identical cover plate assembly is used on end plate  30 . A shoulder bearing  156  is provided in a hole  159  for the drive shaft (not shown in FIG. 2) coupled with each gear pump  20 . When cover plate  150  is removed, the drive shaft may be pulled out of one or more of the gear pumps  20  to allow removal of that gear pump  20  from the corresponding manifold segment  14 . A similar bearing  158  is provided in a hole for the drive shaft and a pair of roll pins  162 ,  164  are provided in the opposite end plate  30 . 
     A process air sensor port  170  and a liquid sensor port  172  are provided in bores  174 ,  176  extending through edge portions  178 ,  180  of each end plate  30 ,  32  with the remaining bores  184 ,  186  of the end plates  30 ,  32  receiving plugs (not shown), as necessary. Ports  170 ,  172  receive temperature sensors  188 ,  189  for respectively measuring the temperatures of the process air section, i.e., lower section of each end plate  30 ,  32  and the liquid section, i.e., upper section of each end plate  30 ,  32 . The upper and lower sections are divided by insulators which, in this preferred embodiment, comprise pairs of slots  190 ,  192  and  194 ,  196  and pairs of holes  202 ,  204  and  206 ,  208 . These air spaces therefore provide thermal insulation between the upper section and lower section and allow these respective sections to be maintained at different operating temperatures. It will be appreciated that other types of insulators and insulating materials may be used as well. 
     As further shown in FIG. 3, each gear pump  20  comprises a conventional sandwiched construction of three plates  220 ,  222 ,  224  containing a pair of gears  230 ,  232 . One gear is an idler gear  230 , while the other gear is a driven gear  232  which receives a drive shaft  234  having a hexagonal cross section. It will be appreciated that drive shaft  234  extends through each gear pump  20  and is received in a complimentary hexagonally-shaped bore of each drive gear  232 . A static seal  240  contains any liquid which would otherwise tend to seep out of gear pump  20 . A rupture disc assembly  242  is provided for providing pressure relief in the event of a significant over-pressure condition. On the back side of each gear pump  20 , one port  244  is threaded to receive a temperature sensor (not shown). This is especially useful during start-up to ensure that each gear pump  20  is heated to the application temperature before operation. This threaded port  244  may also receive an extractor tool (not shown) for removing the gear pump  20  from the associated manifold segment  14  during repair or replacement without having to dissemble or decouple the manifold segments  14  from one another. The second bore  248  receives a plug assembly  250 , which may be removed to then allow insertion of a pressure transducer (not shown) for reading output liquid pressure. 
     Referring now to FIGS. 4 and 5, each manifold segment  14   a ,  14   b  is identical, except for the fastener configurations used to fasten manifold segments  14   a ,  14   b  together. In this regard, manifold segment  14   a  includes four counterbored fastener holes  258  for receiving four fasteners  260 , while the corresponding holes  262  in an adjacent manifold segment  14   b  are threaded to receive the threaded portions of fasteners  260 . Likewise, manifold segment  14   b  includes four counterbored fastener holes  264  for receiving four fasteners  268  and the threaded portions of these fasteners  268  are received in threaded holes  270  in an adjacent manifold segment  14   a  as shown in FIG.  4 . As previously described, a plurality of radially spaced bores  126  direct process air in a serpentine, back-and-forth manner along the length of dispenser assembly (FIG. 1) so that the process air is heated as it traverses back-and-forth alongside the heater rod  60   a  contained in hole  67 . A slot  280  and a hole  282 , as well as a pair of recesses  284 ,  286  are provided for thermally isolating the lower process air section of each manifold segment  14 ,  14   b  from the upper liquid section of each manifold segment  14   a ,  14   b  in a manner similar to that discussed in connection with the end plates  30 ,  32 . The recess  290  in the back side of each manifold segment  14   a ,  14   b  receives a gear pump  20 . A diverter plate  298  (only one shown) is secured to each manifold segment  14   a ,  14   b  with a fastener  300  and may be configured to direct the liquid in various manners. In the preferred embodiment shown, liquid is directed from liquid material input passage  140  into aligned supply bores  301  in a manifold segments  14   a ,  14   b . The liquid is then directed into an internal passage (not shown) and into a bore  302  in each diverter plate  298 . Bore  302  communicates with a supply passage  303  in the associated gear pump  20  (FIG. 1) connected gear pump  20  (FIG. 1) and exits from the gear pump  20  through a discharge passage  305  of gear pump  20  and into a bore  304  communicating with a discharge passage  306  at a front edge portion  308  of the manifold segment  14   a . Passage  306  supplies the pressurized liquid to the associated dispensing module  16 . Another passage  307  is a recirculation passage which receives liquid from the associated dispensing module  16  when the module  16  is OFF. Passage  307  communicates with supply passage  301 . Each gear pump  20  is held on with a clamp  320  and fastener  322 . Clamp  320  includes upper and lower angled surfaces  320   a ,  320   b  acting as cam surfaces to engage complimentary surfaces at lower edges of the gear pump  20  and the manifold segment  14   a , respectively. Another bore  326  in the clamp  320  is provided for receiving a bayonet process air sensor (not shown) as described in connection with FIG.  2 . 
     As further shown in FIGS. 4 and 5, two passages  332 ,  334  are provided on front edge  308  of each manifold segment  14   a ,  14   b . Passages  332 ,  334  supply pressurized control air to the associated dispensing module  16  for pneumatically actuating a piston within module  16  between open and closed positions. Referring to FIG. 6A, for the preferred embodiment in which each manifold segment  14  (FIG. 1) is controlled by a separate air control valve  18 , a gasket  340  is placed between manifold segment  14  and air control valve  18 . Gasket  340  includes a lower surface  342  and an upper surface  344 . An air supply hole  346  is centrally located and communicates with air supply port  82 . Hole  346  is flanked by air distribution passages  348 ,  350  which respectively communicate with passages  332 ,  334  after assembly onto manifold segment  14 . Respective air exhaust passages  352 ,  354  respectively communicate with exhaust ports  92   a ,  94   a  after assembly. More specifically referring to FIGS. 4 and 5, holes  346 ,  348 ,  350 ,  352 ,  354  respectively align with holes or passages  356 ,  358 ,  360 ,  362 ,  364  on top of the associated manifold segment  14   a  or  14   b . Manifold segments  14   a ,  14   b  further include an air supply port  374  which communicates with passage  356  and exhaust ports  376 ,  380  which respectively communicate with passages  362 ,  364 . Passages  370 ,  372  are also provided for an optional manifold segment to manifold segment distribution of control air if only one air control valve  18  is to be used to operate a plurality of dispensing modules  16 . 
     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 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, wherein we claim: