Abstract:
A nozzle, which is for in at least one embodiment a hot glue gun, has a resilient cap that is positioned within the nozzle&#39;s conduit. The resilient cap has at least one slit that serves as a check valve. The invention solves the problem of resilient caps in hot glue guns becoming unseated and wedging in the tapering section of the glue gun nozzle conduit by adding a collar inside the conduit that prevents the base section of the resilient cap from wedging in deeper into the nozzle&#39;s conduit, which would otherwise make the valve fail.

Description:
BACKGROUND 
     Flowable adhesives are typically supplied in a container (e.g., a tube) fitted with a nozzle. In use, adhesive flows from the container through the nozzle and is applied to an intended substrate. In the case of reactive adhesives, the adhesive has a tendency to cure in the nozzle causing it to clog. Moreover, in the case of flowable adhesives, there is often a tendency of the adhesive to drip or ooze (e.g., depending on its viscosity) from the nozzle between applications. 
     To overcome the problem of dripping or oozing, valves have been placed within the nozzle. Many valves in commercial use have multiple machined or cast metallic parts and are costly. Valves of this type can easily become inoperative due to the properties of the adhesive used. Due to their cost, much effort is put into keeping these valves (and hence nozzles) operational, especially when using curing/drying adhesives. 
     One known approach to overcoming the foregoing problems is embodied in the prior art nozzle useful for dispensing some flowable adhesives shown in  FIGS. 1A and 1B . Referring now to  FIGS. 1A and 1B , prior art nozzle  100  has a hollow body  105  made of polypropylene. An internal wall surface  110  defines a tubular conduit  120 , which extends from an inlet port  145  to a dispensing port  140 . Internal wall surface  110  has a cylindrical portion  112  adjacent a frustoconical portion  118 . A vinyl resilient cap  150  snugly contacts frustoconical portion  118  of internal wall surface  110 . The vinyl resilient cap  150  has an annular sidewall  160  extending from a circular base  170  that has a slit  180  therein. Prior art nozzle  100  also has screw threads  132  formed in the internal wall surface  110  adjacent inlet port  145 , flange  134  proximate inlet port  145 , and reinforcing ribs  107  formed on an exterior surface of the nozzle  100 . 
     SUMMARY 
     In one aspect, the present disclosure relates to a nozzle comprising: a hollow body comprising an internal wall surface defining a conduit, the conduit extending from an inlet port to a dispensing port, and at least a portion of the internal wall surface having consecutively: a substantially cylindrical barrel, a substantially frustoconical cap seat, a collar, and a dispensing tube; a resilient cap snugly contacting the substantially frustoconical cap seat, the resilient cap comprising an annular sidewall extending from a circular base, the circular base having at least one slit therein, wherein the resilient cap is oriented with the circular base toward the collar. In certain embodiments, the nozzle is thermally stable at a temperature of at least 240 degrees Fahrenheit (i.e., ° F.). In certain embodiments, the nozzle is thermally stable at a temperature of 300° F. 
     In certain embodiments, the resilient cap comprises an elastomer. In certain embodiments, the resilient cap comprises vinyl. In certain embodiments, the resilient cap has a central nib and at least one slit is disposed at least partially within the central nib. In certain embodiments, at least one slit comprises a cut. 
     In certain embodiments, the hollow body further comprises an exterior surface comprising reinforcing ribs. In certain embodiments, the hollow body comprises a polymeric material (e.g., a polyacetal). In certain embodiments, the hollow body further comprises: a flange proximate the inlet port; and screw threads formed in the internal wall surface adjacent the inlet port. 
     Nozzles according to the present disclosure are useful, for example, for dispensing flowable adhesives, and especially viscous flowable adhesives that are heated (e.g., to a temperature of at least 240° F.) in order to dispense them. 
     We discovered that prior art nozzle  100  shown in  FIGS. 1A and 1B  frequently plugs if used with viscous adhesives at 240° F. Without wishing to be bound by theory, we believe that the vinyl resilient cap  150  softens and deforms resulting in it progressing down the conduit to a point where compression from the inner wall surface closes the slit. In contrast, nozzles according to the present disclosure typically do not exhibit this problem. Moreover, if used for dispensing viscous flowable adhesives, nozzles according to the present disclosure typically don&#39;t drip or ooze, and can in many instances be manufactured inexpensively enough to be disposable. 
     Accordingly, in another aspect, the present disclosure relates to an adhesive dispenser comprising: a container enclosing a reducible cavity containing a flowable adhesive, the reducible cavity fluidly connected to the inlet port of a nozzle according to the present disclosure. 
     In certain embodiments, the container further comprises a threaded outlet port, wherein the hollow body of the nozzle further comprises: a flange proximate the inlet port; and screw threads formed in the internal wall surface adjacent the inlet port, wherein the threaded outlet port threadably engages the screw threads formed in the internal wall surface. In certain embodiments, the flowable adhesive comprises a viscous reactive adhesive. In certain embodiments, the flowable adhesive comprises a polyurethane reactive adhesive. 
     In yet another aspect, the present disclosure relates to a method of dispensing an adhesive, the method comprising dispensing the flowable adhesive from an adhesive dispenser according to the present disclosure. In certain embodiments, at least a portion of the flowable adhesive is heated to a temperature in a range of from 240 to 300° F. 
     As used herein: 
     the term “downstream” refers to flow from the inlet port to the dispensing port; 
     the term “elastomer” refers to an elastic polymer; 
     the term “resilient” means returning to, or capable of returning to, an initial shape after mechanical deformation; 
     the term “slit” refers to a narrow cut or opening, which may be long or short, and which may be straight or curved; 
     the terms “snug contact” and “snugly contacting” mean that the two items in contact are frictionally held in place regardless of orientation of the nozzle. 
     the term “substantially cylindrical barrel” means that the barrel has a cylindrical appearance but allows for minor deviations in shape, for example, as resulting from tolerances in manufacturing; 
     the term “substantially frustoconical cap seat” means that the cap seat has a frustoconical appearance but allows for minor deviations in shape, for example, as resulting from tolerances in manufacturing; 
     the term “thermally stable” in reference to a given temperature means not deformed (e.g., by softening or melting) or otherwise decomposed by heating at that temperature; and 
     the term “oriented toward” means oriented in a position facing. 
     Certain advantages of various nozzles according to the present disclosure are more fully shown and described in the drawings and detailed description below wherein like reference numerals are used to represent similar parts. It is to be understood, however, that the description and drawings are for the purposes of illustration only and should not be read in a manner that would unduly limit the scope of this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1A  is a cross-sectional side view of the prior art nozzle shown in  FIG. 1B ; 
         FIG. 1B  is a perspective view of the prior art nozzle shown in  FIG. 1A ; 
         FIG. 2A  is a cross-sectional side view of an exemplary nozzle according to one embodiment of the present disclosure, shown in  FIG. 2B ; 
         FIG. 2B  is a perspective view of the exemplary nozzle shown in  FIG. 2A ; 
         FIG. 2C  is a perspective view of resilient cap  250 ; and 
         FIG. 3  is a perspective view of an adhesive dispenser according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 2A , exemplary nozzle  200  according to one embodiment of the present disclosure comprises hollow body  205  comprising an internal wall surface  210  defining a conduit  220 . Conduit  220  is substantially tubular and extends from inlet port  245  to dispensing port  240 . A portion of internal wall surface  210  has consecutively: a substantially cylindrical barrel  212  (hereinafter referred to as the “barrel”), a substantially frustoconical cap seat  214  (hereinafter referred to as the “cap seat”), collar  216 , and a dispensing tube  218 . Resilient cap  250  snugly contacts cap seat  214 . Resilient cap  250  comprises annular sidewall  260  extending from a circular base  270  that has slit  280  therein. As shown, circular base has optional central nib  265 . Resilient cap  250  is oriented with circular base  270  toward collar  216 . 
     In some embodiments, nozzles according to the present disclosure are thermally stable at temperatures at or above 240° F. or even at or above 300° F., which allows them to be successfully used to dispense adhesives that have sufficiently high viscosity that they require heating to such temperatures in order to dispense them effectively. 
     The hollow body may be formed of any material that is thermally stable at temperatures of at least from 240° F. to 300° F., or higher. Suitable materials may be selected from, e.g., metal, glass, and polymeric materials such as thermoplastics and thermosets, as well as combinations thereof. Polymeric materials may be combined with one or more additives such as, for example, filler(s), toughener(s), plasticizer(s), flame retardant(s), antioxidant(s), colorant(s), processing aid(s), and/or mold release agent(s). In some embodiments, e.g., for disposable applications, the hollow body may comprise an injection molded polymeric material. 
     Examples of useful polymeric materials include: polyacetals such as those acetal resins available from E. I. du Pont de Nemours &amp; Co. under the trade designation “DELRIN”; acrylonitrile butadiene styrene (ABS); polycarbonates (PC); polyamides (PA); high impact polystyrene (HIPS); polybutylene terephthalate (PBT); polyethylene terephthalate (PET); polyphenylene oxide (PPO); polysulphone (PSU); polyetherketone (PEK); polyetheretherketone (PEEK); and polyimides. 
     The barrel serves to convey adhesive from the inlet port into the remainder of the conduit. The barrel may have any length and/or diameter. In general, the barrel should have an inner diameter sufficient to permit passage of the resilient cap to the cap seat during fabrication. 
     The cap seat narrows the conduit relative to the barrel. Depending on the shape of the resilient cap the cap seat may have any taper angle, however, typically a taper angle of from 5 to 20 degrees is generally useful for achieving snug contact between the resilient cap and the cap seat. In general, higher taper angles (e.g., taper angles greater than about 60 degrees) may tend to make achieving such snug contact more difficult. 
     The collar serves to prevent the resilient cap from traveling sufficiently far into the dispensing tube to cause plugging during use under at least some conditions. Typically, the collar is formed at an abrupt angle relative to the cap seat. For example, the collar may comprise a disk oriented perpendicularly to a longitudinal rotational axis of the barrel. It is envisioned that other similar shapes may also be used. While the collar may have any dimensions (e.g., thickness and/or inner diameter) depending typically on the particular choice of resilient cap and conduit dimensions, any reduction in the diameter of the downstream end of the cap seat may be used. For example, the collar may reduce the diameter of the downstream end of the cap seat by at least 10, 20, 30, or even 40 percent, or more. However, excessive reduction in the diameter (e.g., to a point where the collar blocks a portion of the slit(s) in the resilient cap valve) will typically limit the flow capacity through the slit(s). 
     The dispensing tube may have any size or shape. For example, it may be conical in its entirety or for only a portion thereof. In some embodiments it may be straight and in other embodiments bent. The outlet port may have any desired shape (e.g., a circle, an ellipse, or a slot). 
     The nozzle may further comprise various optional features. Referring again to  FIGS. 2A and 2B , exemplary optional features include: screw threads  232  formed in the internal wall surface adjacent the inlet port (e.g., to provide a secure fluid connection to an adhesive-filled container such as a cartridge); flange  234  proximate the inlet port (e.g., to provide strength to the inlet port and/or sealing); and reinforcing ribs  207  (see  FIG. 2B ) formed on an exterior surface of the nozzle opposite the barrel (e.g., to provide dimensional stability (e.g., against bending) and/or provide a gripping surface for screwing the nozzle onto an adhesive-filled container such as a cartridge. 
     The resilient cap is first of all resilient. It may comprise any resilient material that is impermeable to at least one adhesive, is capable of effecting a seal between the resilient cap and the cap seat, and enables the slit(s) in the resilient cap to regulate passage of adhesive into the dispensing tube during normal use. Examples of suitable materials include polymeric materials such as vinyl (e.g., plasticized polyvinyl chloride) and elastomers (e.g., natural rubbers, or synthetic rubbers such as silicones, styrene-butadiene rubbers, EPDM rubbers, or chloroprene rubbers). Polymeric materials having a Shore A hardness in a range of from 60 to 80 are typically useful for forming the resilient cap, although this is not a requirement. The resilient cap may be formed, for example, using molding techniques well known in the art or obtained form commercial sources. 
     The sidewall of the resilient cap typically has a substantially uniform thickness, although variation in uniformity of the wall thickness is permissible. The sidewall and circular base may have any thickness, typically depending on the composition of the resilient cap, as long as the resilient cap remains sufficiently flexible to form a seal with the cap seat and/or collar. For example, for use with a hollow body as shown in  FIG. 2A  having an overall conduit length 4.050 inches, the cap may have a height in a range of from 0.55 to 0.67 inches (e.g., 0.608 inches) and diameter in a range of from 0.461 to 0.475 inches (e.g., 0.468 inches), and the sidewall may have a thickness in a range of from 0.055 to 0.070 inches (e.g., 0.062 inches), the circular base may have a thickness in a range of from 0.085 to 0.100 inches (e.g., 0.093 inches). 
     The circular base may be essentially flat or domed (e.g., hemispherical), although other shapes are also permissible. Moreover, the circular base may optionally comprise a nib (e.g., shown as  265  in  FIG. 2C ). Such nibs may be, for example, hemispherical, conical, or some other shape. 
     In general, the resilient cap may have a wide variety of shapes (e.g., substantially cylindrical, substantially frustoconical, or as shown in  FIGS. 2A-2C ) as long as it is of sufficient dimensions to snugly contact the cap seat. 
     The slit(s) may have any shape (e.g., linear or arcuate) and any length(s). Multiple slits may be arranged in any manner (e.g., a cross or a star). The slit(s) in the resilient cap expand (e.g., forming an opening or enlarging an existing opening) during use as pressure is applied to flowable material dispensed through the nozzle. As the pressure applied to the flowable material decreases, the slit(s) tend to close (e.g., at least partially close). Accordingly, they regulate flow and will typically be sized depending on the intended use. The slit(s) may be closed, open, or partially open. 
     In some embodiments, nozzles according to the present disclosure are useful in the manufacture of adhesive dispensers. An exemplary adhesive dispenser is shown in  FIG. 3 . Adhesive dispenser  300  has nozzle  200  threadably engaged to an adhesive container  310  (shown as a cartridge tube) enclosing a reducible cavity (not shown) filled with a flowable adhesive (e.g., a polyurethane reactive adhesive, not shown). The engaged nozzle/container assembly is disposed within adhesive applicator  305 . Adhesive applicator  305  further includes an optional heat source  340  that may heat the flowable adhesive to achieve a desired viscosity. In use, compressed air  307  is used to shrink the volume of the reducible cavity thereby forcing the flowable adhesive into and through nozzle  200 . Such adhesive dispensers are useful for, e.g., applying viscous adhesives, and especially those that must be heated in order to have appreciable flowability. 
     Nozzles according to the present disclosure may be used, for example, in combination with commercially available adhesive applicators such as, for example, “3M SCOTCH-WELD POLYURETHANE REACTIVE ADHESIVE APPLICATOR, 62-9895-9930-3 (250 DEG F, GREY)”, “3M SCOTCH-WELD POLYURETHANE REACTIVE (PUR) EASY ADHESIVE APPLICATOR, 62-9845-9930-8 (170 DEG F, GREEN)”, and “3M SCOTCH-WELD POLYURETHANE REACTIVE (PUR) EASY 250 ADHESIVE APPLICATOR, 62-9865-9930-6 (250 DEG F, YELLOW)”. 
     Various modifications and alterations of this invention may be made by those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.